diff --git a/client/src/app/core/services/projector.service.ts b/client/src/app/core/services/projector.service.ts
index 682c03b1b..6926cc35a 100644
--- a/client/src/app/core/services/projector.service.ts
+++ b/client/src/app/core/services/projector.service.ts
@@ -39,41 +39,11 @@ export class ProjectorService extends OpenSlidesComponent {
     }
 
     /**
-     * Checks, if a given object is projected.
+     * Retusn the identifiable projector element from the given types of slides/elements/descriptors
      *
-     * @param obj The object in question
-     * @returns true, if the object is projected on one projector.
+     * @param obj Something related to IdentifiableProjectorElement
+     * @returns the identifiable projector element from obj.
      */
-    public isProjected(obj: Projectable | ProjectorElementBuildDeskriptor): boolean {
-        if (isProjectable(obj)) {
-            return this.DS.getAll<Projector>('core/projector').some(projector => {
-                return projector.isElementShown(obj.getSlide().getBasicProjectorElement());
-            });
-        } else {
-            return this.DS.getAll<Projector>('core/projector').some(projector => {
-                return projector.isElementShown(obj.getBasicProjectorElement());
-            });
-        }
-    }
-
-    /**
-     * Get all projectors where the object is prejected on.
-     *
-     * @param obj The object in question
-     * @return All projectors, where this Object is projected on
-     */
-    public getProjectorsWhichAreProjecting(obj: Projectable | ProjectorElementBuildDeskriptor): Projector[] {
-        if (isProjectable(obj)) {
-            return this.DS.getAll<Projector>('core/projector').filter(projector => {
-                return projector.isElementShown(obj.getSlide().getBasicProjectorElement());
-            });
-        } else {
-            return this.DS.getAll<Projector>('core/projector').filter(projector => {
-                return projector.isElementShown(obj.getBasicProjectorElement());
-            });
-        }
-    }
-
     private getProjectorElement(
         obj: Projectable | ProjectorElementBuildDeskriptor | IdentifiableProjectorElement
     ): IdentifiableProjectorElement {
@@ -86,6 +56,34 @@ export class ProjectorService extends OpenSlidesComponent {
         }
     }
 
+    /**
+     * Checks, if a given object is projected.
+     *
+     * @param obj The object in question
+     * @returns true, if the object is projected on one projector.
+     */
+    public isProjected(obj: Projectable | ProjectorElementBuildDeskriptor | IdentifiableProjectorElement): boolean {
+        const element = this.getProjectorElement(obj);
+        return this.DS.getAll<Projector>('core/projector').some(projector => {
+            return projector.isElementShown(element);
+        });
+    }
+
+    /**
+     * Get all projectors where the object is prejected on.
+     *
+     * @param obj The object in question
+     * @return All projectors, where this Object is projected on
+     */
+    public getProjectorsWhichAreProjecting(
+        obj: Projectable | ProjectorElementBuildDeskriptor | IdentifiableProjectorElement
+    ): Projector[] {
+        const element = this.getProjectorElement(obj);
+        return this.DS.getAll<Projector>('core/projector').filter(projector => {
+            return projector.isElementShown(element);
+        });
+    }
+
     /**
      * Checks, if the object is projected on the given projector.
      *
@@ -101,12 +99,8 @@ export class ProjectorService extends OpenSlidesComponent {
     }
 
     /**
-     * Projects the given ProjectorElement on the given projectors.
-     *
-     * TODO: this does not care about the element being stable. Some more logic must be added later.
-     *
-     * On the given projectors: Delete all non-stable elements and add the given element.
-     * On all other projectors: If the element (compared with name and id) is there, it will be deleted.
+     * Projects the given ProjectorElement on the given projectors. Removes the element
+     * from all non-given projectors
      *
      * @param projectors All projectors where to add the element.
      * @param element The element in question.
@@ -121,6 +115,13 @@ export class ProjectorService extends OpenSlidesComponent {
         });
     }
 
+    /**
+     * Projcets the given object on the projector. If the object is non-stable, all other non-stable
+     * elements will be removed and added to the history.
+     *
+     * @param projector The projector to add the object to.
+     * @param obj The object to project
+     */
     public async projectOn(
         projector: Projector,
         obj: Projectable | ProjectorElementBuildDeskriptor | IdentifiableProjectorElement
@@ -147,26 +148,40 @@ export class ProjectorService extends OpenSlidesComponent {
         }
     }
 
+    /**
+     * Removes the given object from the projector. Non stable elements will be added to the history.
+     *
+     * @param projector The projector
+     * @param obj the object to unproject
+     */
     public async removeFrom(
         projector: Projector,
         obj: Projectable | ProjectorElementBuildDeskriptor | IdentifiableProjectorElement
     ): Promise<void> {
         const element = this.getProjectorElement(obj);
 
-        if (element.stable) {
-            // Just remove this stable element
-            projector.removeElements(element);
-            await this.projectRequest(projector, projector.elements);
-        } else {
-            // For non-stable elements remove all current non-stable elements and add them to the history
-            const removedElements = projector.removeElements(element);
-            if (removedElements.length > 0) {
-                console.log(projector.elements, removedElements);
+        const removedElements = projector.removeElements(element);
+        if (removedElements.length > 0) {
+            if (element.stable) {
+                await this.projectRequest(projector, projector.elements);
+            } else {
+                // For non-stable elements: Add removed elements to the history.
                 await this.projectRequest(projector, projector.elements, null, removedElements);
             }
         }
     }
 
+    /**
+     * Executes the request to change projector elements.
+     *
+     * Note: Just one of `appendToHistory` and `deleteLastHistoryElement` can be given.
+     *
+     * @param projector The affected projector
+     * @param elements (optional) Elements to set.
+     * @param preview (optional) preview to set
+     * @param appendToHistory (optional) Elements to be appended to the history
+     * @param deleteLastHistroyElement (optional) If given, the last history element will be removed.
+     */
     private async projectRequest(
         projector: Projector,
         elements?: ProjectorElements,
@@ -206,21 +221,41 @@ export class ProjectorService extends OpenSlidesComponent {
         });
     }
 
+    /**
+     * Returns a model associated with the identifiable projector element. Throws an error,
+     * if the element is not mappable.
+     *
+     * @param element The projector element
+     * @returns the model from the projector element
+     */
     public getModelFromProjectorElement<T extends BaseModel>(element: IdentifiableProjectorElement): T {
         if (!this.slideManager.canSlideBeMappedToModel(element.name)) {
-            throw new Error('THis projectorelement cannot be mapped to a model');
+            throw new Error('This projector element cannot be mapped to a model');
         }
         const identifiers = element.getIdentifiers();
-        if (!identifiers.includes('name') || !identifiers.includes('name')) {
+        if (!identifiers.includes('name') || !identifiers.includes('id')) {
             throw new Error('To map this element to a model, a name and id is needed.');
         }
         return this.DS.get<T>(element.name, element.id);
     }
 
+    /**
+     * Projects the next slide in the queue. Moves all currently projected
+     * non-stable slides to the history.
+     *
+     * @param projector The projector
+     */
     public async projectNextSlide(projector: Projector): Promise<void> {
         await this.projectPreviewSlide(projector, 0);
     }
 
+    /**
+     * Projects one slide (given by the index of the preview) on the given projector. Moves
+     * all current projected non-stable elements to the history.
+     *
+     * @param projector The projector
+     * @param previewIndex The index in the `elements_preview` array.
+     */
     public async projectPreviewSlide(projector: Projector, previewIndex: number): Promise<void> {
         if (projector.elements_preview.length === 0 || previewIndex >= projector.elements_preview.length) {
             return;
@@ -231,6 +266,11 @@ export class ProjectorService extends OpenSlidesComponent {
         await this.projectRequest(projector, projector.elements, projector.elements_preview, removedElements);
     }
 
+    /**
+     * Projects the last slide of the history. This slide will be removed from the history.
+     *
+     * @param projector The projector
+     */
     public async projectPreviousSlide(projector: Projector): Promise<void> {
         if (projector.elements_history.length === 0) {
             return;
@@ -253,10 +293,21 @@ export class ProjectorService extends OpenSlidesComponent {
         await this.projectRequest(projector, projector.elements, projector.elements_preview, null, true);
     }
 
+    /**
+     * Saves the preview of the projector
+     *
+     * @param projector The projector to save the preview.
+     */
     public async savePreview(projector: Projector): Promise<void> {
         await this.projectRequest(projector, null, projector.elements_preview);
     }
 
+    /**
+     * Appends the given element to the preview.
+     *
+     * @param projector The projector
+     * @param element The element to add to the preview.
+     */
     public async addElementToPreview(projector: Projector, element: ProjectorElement): Promise<void> {
         projector.elements_preview.push(element);
         await this.projectRequest(projector, null, projector.elements_preview);
diff --git a/client/src/app/core/services/servertime.service.ts b/client/src/app/core/services/servertime.service.ts
index 44a0f54c4..dc2068900 100644
--- a/client/src/app/core/services/servertime.service.ts
+++ b/client/src/app/core/services/servertime.service.ts
@@ -5,6 +5,13 @@ import { HttpService } from './http.service';
 import { environment } from 'environments/environment.prod';
 import { BehaviorSubject, Observable } from 'rxjs';
 
+/**
+ * This service provides the timeoffset to the server and a user of this service
+ * can query the servertime.
+ *
+ * This service needs to be started with `startScheduler` which will update
+ * the servertime frequently.
+ */
 @Injectable({
     providedIn: 'root'
 })
@@ -13,7 +20,7 @@ export class ServertimeService extends OpenSlidesComponent {
     private static NORMAL_TIMEOUT = 60 * 5;
 
     /**
-     * In milliseconds
+     * The server offset in milliseconds
      */
     private serverOffsetSubject = new BehaviorSubject<number>(0);
 
@@ -21,27 +28,40 @@ export class ServertimeService extends OpenSlidesComponent {
         super();
     }
 
+    /**
+     * Starts the scheduler to sync with the server.
+     */
     public startScheduler(): void {
         this.scheduleNextRefresh(0);
     }
 
+    /**
+     * Get an observable for the server offset.
+     */
     public getServerOffsetObservable(): Observable<number> {
         return this.serverOffsetSubject.asObservable();
     }
 
+    /**
+     * Schedules the next sync with the server.
+     *
+     * @param seconds The timeout in seconds to the refresh.
+     */
     private scheduleNextRefresh(seconds: number): void {
         setTimeout(async () => {
             let timeout = ServertimeService.NORMAL_TIMEOUT;
             try {
                 await this.refreshServertime();
             } catch (e) {
-                console.log(e);
                 timeout = ServertimeService.FAILURE_TIMEOUT;
             }
             this.scheduleNextRefresh(timeout);
         }, 1000 * seconds);
     }
 
+    /**
+     * Queries the servertime and calculates the offset.
+     */
     private async refreshServertime(): Promise<void> {
         // servertime is the time in seconds.
         const servertime = await this.http.get<number>(environment.urlPrefix + '/core/servertime/');
@@ -52,6 +72,9 @@ export class ServertimeService extends OpenSlidesComponent {
         this.serverOffsetSubject.next(Math.floor(Date.now() - servertime * 1000));
     }
 
+    /**
+     * Calculate the time of the server.
+     */
     public getServertime(): number {
         return Date.now() - this.serverOffsetSubject.getValue();
     }
diff --git a/client/src/app/shared/components/projector-button/projector-button.component.ts b/client/src/app/shared/components/projector-button/projector-button.component.ts
index be596fed8..ac6c678de 100644
--- a/client/src/app/shared/components/projector-button/projector-button.component.ts
+++ b/client/src/app/shared/components/projector-button/projector-button.component.ts
@@ -1,10 +1,19 @@
 import { Component, OnInit, Input } from '@angular/core';
 
-import { Projectable, ProjectorElementBuildDeskriptor } from 'app/site/base/projectable';
+import {
+    Projectable,
+    ProjectorElementBuildDeskriptor,
+    isProjectable,
+    isProjectorElementBuildDeskriptor
+} from 'app/site/base/projectable';
 import { ProjectionDialogService } from 'app/core/services/projection-dialog.service';
 import { ProjectorService } from '../../../core/services/projector.service';
 
 /**
+ * The projector button to project something on the projector.
+ *
+ * Use the input [object] to specify the object to project. It can either be
+ * a Projectable or a ProjectorElementBuildDeskriptor
  */
 @Component({
     selector: 'os-projector-button',
@@ -12,11 +21,29 @@ import { ProjectorService } from '../../../core/services/projector.service';
     styleUrls: ['./projector-button.component.scss']
 })
 export class ProjectorButtonComponent implements OnInit {
+    /**
+     * The object to project.
+     */
+    private _object: Projectable | ProjectorElementBuildDeskriptor;
+
+    public get object(): Projectable | ProjectorElementBuildDeskriptor {
+        return this._object;
+    }
+
     @Input()
-    public object: Projectable | ProjectorElementBuildDeskriptor;
+    public set object(obj: Projectable | ProjectorElementBuildDeskriptor) {
+        if (isProjectable(obj) || isProjectorElementBuildDeskriptor(obj)) {
+            this._object = obj;
+        } else {
+            console.error(
+                'Your model for the projectorbutton is not projectable and not' + 'a projectorElementBuildDescriptor!',
+                obj
+            );
+        }
+    }
 
     /**
-     * The consotructor
+     * The constructor
      */
     public constructor(
         private projectionDialogService: ProjectionDialogService,
@@ -28,6 +55,11 @@ export class ProjectorButtonComponent implements OnInit {
      */
     public ngOnInit(): void {}
 
+    /**
+     * Click on the projector button
+     *
+     * @param event  the click event
+     */
     public onClick(event: Event): void {
         event.stopPropagation();
         this.projectionDialogService.openProjectDialogFor(this.object);
@@ -39,10 +71,9 @@ export class ProjectorButtonComponent implements OnInit {
      * @returns true, if the object is projected on one projector.
      */
     public isProjected(): boolean {
-        if (this.object) {
-            return this.projectorService.isProjected(this.object);
-        } else {
+        if (!this.object) {
             return false;
         }
+        return this.projectorService.isProjected(this.object);
     }
 }
diff --git a/client/src/app/shared/models/core/projector.ts b/client/src/app/shared/models/core/projector.ts
index 13a5f4acb..689ea8592 100644
--- a/client/src/app/shared/models/core/projector.ts
+++ b/client/src/app/shared/models/core/projector.ts
@@ -84,8 +84,12 @@ export class Projector extends BaseModel<Projector> {
      * @returns all removed unstable elements
      */
     public removeAllNonStableElements(): ProjectorElements {
-        const unstableElements = this.elements.filter(element => !element.stable);
-        this.elements = this.elements.filter(element => element.stable);
+        let unstableElements: ProjectorElements;
+        let stableElements: ProjectorElements;
+
+        [unstableElements, stableElements] = this.partitionArray(this.elements, element => !element.stable);
+
+        this.elements = stableElements;
         return unstableElements;
     }
 
@@ -99,8 +103,11 @@ export class Projector extends BaseModel<Projector> {
     }
 
     /**
-     * Must match everything. If a projectorelement does not have all keys
-     * to identify, it will be removed, if all existing keys match
+     * Removes and returns all projector elements, witch can be identified with the
+     * given element.
+     *
+     * @param element The element to remove
+     * @returns all removed projector elements
      */
     public removeElements(element: IdentifiableProjectorElement): ProjectorElements {
         let removedElements: ProjectorElements;
@@ -114,6 +121,14 @@ export class Projector extends BaseModel<Projector> {
         return removedElements;
     }
 
+    /**
+     * Splits up the array into two arrays. All elements with a true return value from the callback
+     * will be in the fist array, all others in the second one.
+     *
+     * @param array The array to split
+     * @param callback To evaluate every entry
+     * @returns the splitted array
+     */
     private partitionArray<T>(array: T[], callback: (element: T) => boolean): [T[], T[]] {
         return array.reduce(
             (result, element) => {
diff --git a/client/src/app/site/common/components/countdown-list/countdown-list.component.ts b/client/src/app/site/common/components/countdown-list/countdown-list.component.ts
index ed4ee140e..bca61da4b 100644
--- a/client/src/app/site/common/components/countdown-list/countdown-list.component.ts
+++ b/client/src/app/site/common/components/countdown-list/countdown-list.component.ts
@@ -69,7 +69,7 @@ export class CountdownListComponent extends BaseViewComponent implements OnInit
     }
 
     /**
-     * Add a new Section.
+     * Add a new countdown.
      */
     public onPlusButton(): void {
         if (!this.countdownToCreate) {
diff --git a/client/src/app/site/common/components/projectormessage-list/projectormessage-list.component.ts b/client/src/app/site/common/components/projectormessage-list/projectormessage-list.component.ts
index 6effe7ada..db9bb9b92 100644
--- a/client/src/app/site/common/components/projectormessage-list/projectormessage-list.component.ts
+++ b/client/src/app/site/common/components/projectormessage-list/projectormessage-list.component.ts
@@ -7,7 +7,7 @@ import { BaseViewComponent } from '../../../base/base-view';
 import { MatSnackBar } from '@angular/material';
 
 /**
- * List view for the statute paragraphs.
+ * List view for the projector messages.
  */
 @Component({
     selector: 'os-projectormessage-list',
@@ -22,7 +22,7 @@ export class ProjectorMessageListComponent extends BaseViewComponent implements
     /**
      * Init function.
      *
-     * Sets the title and gets/observes countdowns from DataStore
+     * Sets the title and gets/observes messages from DataStore
      */
     public ngOnInit(): void {
         super.setTitle('Messages');
diff --git a/client/src/app/site/projector/services/current-list-of-of-speakers-slide.service.ts b/client/src/app/site/projector/services/current-list-of-of-speakers-slide.service.ts
index a86229739..bcb9ebdd1 100644
--- a/client/src/app/site/projector/services/current-list-of-of-speakers-slide.service.ts
+++ b/client/src/app/site/projector/services/current-list-of-of-speakers-slide.service.ts
@@ -15,7 +15,7 @@ export class CurrentListOfSpeakersSlideService {
         return {
             name: overlay ? 'agenda/current-list-of-speakers-overlay' : 'agenda/current-list-of-speakers',
             stable: overlay,
-            getIdentifiers: () => ['name', 'stable']
+            getIdentifiers: () => ['name']
         };
     }
 
diff --git a/client/src/app/site/projector/services/projector-data.service.ts b/client/src/app/site/projector/services/projector-data.service.ts
index 3268cc8bf..71a4cb535 100644
--- a/client/src/app/site/projector/services/projector-data.service.ts
+++ b/client/src/app/site/projector/services/projector-data.service.ts
@@ -46,7 +46,7 @@ export class ProjectorDataService {
             Object.keys(update).forEach(_id => {
                 const id = parseInt(_id, 10);
                 if ((<{ error: string }>update[id]).error !== undefined) {
-                    console.log('TODO: Why does the server sends errors on autpupdates?');
+                    console.log('TODO: Why does the server sends errors on autoupdates?');
                 } else {
                     if (this.currentProjectorData[id]) {
                         this.currentProjectorData[id].next(update[id] as ProjectorData);
diff --git a/client/src/app/slides/agenda/current-list-of-speakers/agenda-current-list-of-speakers-slide.component.ts b/client/src/app/slides/agenda/current-list-of-speakers/agenda-current-list-of-speakers-slide.component.ts
index df9b2bc0f..31b21f2d2 100644
--- a/client/src/app/slides/agenda/current-list-of-speakers/agenda-current-list-of-speakers-slide.component.ts
+++ b/client/src/app/slides/agenda/current-list-of-speakers/agenda-current-list-of-speakers-slide.component.ts
@@ -1,9 +1,7 @@
-import { Component, OnInit, Input } from '@angular/core';
+import { Component, OnInit } from '@angular/core';
 
 import { BaseSlideComponent } from 'app/slides/base-slide-component';
-import { HttpService } from 'app/core/services/http.service';
 import { AgendaCurrentListOfSpeakersSlideData } from '../base/agenda-current-list-of-speakers-slide-data';
-import { SlideData } from 'app/site/projector/services/projector-data.service';
 
 @Component({
     selector: 'os-agenda-current-list-of-speakers-slide',
@@ -12,23 +10,8 @@ import { SlideData } from 'app/site/projector/services/projector-data.service';
 })
 export class AgendaCurrentListOfSpeakersSlideComponent extends BaseSlideComponent<AgendaCurrentListOfSpeakersSlideData>
     implements OnInit {
-    private _data: SlideData<AgendaCurrentListOfSpeakersSlideData>;
-
-    public isOverlay: boolean;
-
-    public get data(): SlideData<AgendaCurrentListOfSpeakersSlideData> {
-        return this._data;
-    }
-
-    @Input()
-    public set data(value: SlideData<AgendaCurrentListOfSpeakersSlideData>) {
-        this.isOverlay = !value || value.element.stable;
-        this._data = value;
-    }
-
-    public constructor(private http: HttpService) {
+    public constructor() {
         super();
-        console.log(this.http);
     }
 
     public ngOnInit(): void {
diff --git a/client/src/app/slides/core/clock/core-clock-slide.component.ts b/client/src/app/slides/core/clock/core-clock-slide.component.ts
index 88663d7d3..760be78f5 100644
--- a/client/src/app/slides/core/clock/core-clock-slide.component.ts
+++ b/client/src/app/slides/core/clock/core-clock-slide.component.ts
@@ -32,7 +32,7 @@ export class CoreClockSlideComponent extends BaseSlideComponent<{}> implements O
         const hours = '0' + time.getHours();
         const minutes = '0' + time.getMinutes();
 
-        // Will display time in 10:30:23 format
+        // Will display time in hh:mm format
         this.time = hours.slice(-2) + ':' + minutes.slice(-2);
     }
 
diff --git a/client/src/app/slides/motions/motion/motions-motion-slide.component.html b/client/src/app/slides/motions/motion/motions-motion-slide.component.html
index 73f494852..1b6ed9317 100644
--- a/client/src/app/slides/motions/motion/motions-motion-slide.component.html
+++ b/client/src/app/slides/motions/motion/motions-motion-slide.component.html
@@ -24,7 +24,8 @@
         <div *ngIf="!data.data.is_child" [innerHTML]="data.data.text"></div>
 
         <!-- Amendment text -->
-        <div *ngIf="data.data.is_child" [innerHTML]="data.data.amendment_paragraphs[0]"></div>
+        <div *ngIf="data.data.is_child && data.data.amendment_paragraphs"
+            [innerHTML]="data.data.amendment_paragraphs[0]"></div>
 
         <!-- Reason -->
         <div *ngIf="data.data.reason">
diff --git a/openslides/users/projector.py b/openslides/users/projector.py
index a383d1bfb..ca0d9ee3b 100644
--- a/openslides/users/projector.py
+++ b/openslides/users/projector.py
@@ -23,15 +23,14 @@ def user_slide(all_data: AllData, element: Dict[str, Any]) -> Dict[str, Any]:
     user_id = element.get("id")
 
     if user_id is None:
-        return {"error": "id is required for user slide"}
+        raise ProjectorElementException("id is required for user slide")
 
     try:
         user = all_data["users/user"][user_id]
     except KeyError:
         raise ProjectorElementException(f"user with id {user_id} does not exist")
 
-    return_value = {"user": get_user_name(all_data, user["id"])}
-    return return_value
+    return {"user": get_user_name(all_data, user["id"])}
 
 
 def get_user_name(all_data: AllData, user_id: int) -> str: