diff --git a/client/src/app/shared/components/head-bar/head-bar.component.html b/client/src/app/shared/components/head-bar/head-bar.component.html
index 724f64388..442df3bb1 100644
--- a/client/src/app/shared/components/head-bar/head-bar.component.html
+++ b/client/src/app/shared/components/head-bar/head-bar.component.html
@@ -49,7 +49,7 @@
         </button>
 
         <!-- Save button -->
-        <button mat-button *ngIf="editMode" (click)="save()"><strong translate class="upper">Save</strong></button>
+        <button mat-button *ngIf="editMode" [disabled]="!isSaveButtonEnabled" (click)="save()"><strong translate class="upper">Save</strong></button>
 
         <!-- Menu button slot -->
         <ng-content *ngIf="!editMode" select=".menu-slot"></ng-content>
diff --git a/client/src/app/shared/components/head-bar/head-bar.component.ts b/client/src/app/shared/components/head-bar/head-bar.component.ts
index 4011cb75d..8c0352bde 100644
--- a/client/src/app/shared/components/head-bar/head-bar.component.ts
+++ b/client/src/app/shared/components/head-bar/head-bar.component.ts
@@ -71,6 +71,12 @@ export class HeadBarComponent {
     @Input()
     public editMode = false;
 
+    /**
+     * The save button can manually be disabled.
+     */
+    @Input()
+    public isSaveButtonEnabled = true;
+
     /**
      * Determine multiSelect mode: changed interactions and head bar
      */
diff --git a/client/src/app/shared/validators/custom-validators.ts b/client/src/app/shared/validators/custom-validators.ts
new file mode 100644
index 000000000..1bb858a05
--- /dev/null
+++ b/client/src/app/shared/validators/custom-validators.ts
@@ -0,0 +1,19 @@
+import { ValidatorFn, FormGroup, ValidationErrors } from '@angular/forms';
+
+/**
+ * Constant to validate a `duration` field.
+ *
+ * `([0-9]+)` looks for a number with any length to the `:` (optional).\n
+ *
+ * `([0-5][0-9]?)?`: The user can optionally enter a number for minutes/seconds (0 - 59)
+ *
+ * Afterwards the duration can be specified as hours or minutes (via `[h|m]?` - optional). Defaults to `h`.
+ *
+ * @param control The form-control to validate
+ *
+ * @returns {ValidationErrors | null} Null, if the input is correct, `ValidationErrors` otherwise.
+ */
+export const durationValidator: ValidatorFn = (control: FormGroup): ValidationErrors | null => {
+    const regExp = /^\s*([0-9]+)(:)?([0-5][0-9]?)?\s*[h|m]?$/g;
+    return regExp.test(control.value) || control.value === '' ? null : { valid: false };
+};
diff --git a/client/src/app/site/agenda/components/item-info-dialog/item-info-dialog.component.html b/client/src/app/site/agenda/components/item-info-dialog/item-info-dialog.component.html
index b99c789bb..0aee2a67b 100644
--- a/client/src/app/site/agenda/components/item-info-dialog/item-info-dialog.component.html
+++ b/client/src/app/site/agenda/components/item-info-dialog/item-info-dialog.component.html
@@ -13,6 +13,7 @@
         <!-- Duration -->
         <mat-form-field>
             <input type="string" matInput placeholder="{{ 'Duration' | translate }}" formControlName="durationText" />
+            <mat-error *ngIf="agendaInfoForm.invalid">Your input does not match the following structure 'hh:mm'...</mat-error>
         </mat-form-field>
 
         <!-- Item number (prefix) -->
@@ -34,6 +35,6 @@
     </form>
 </div>
 <div mat-dialog-actions>
-    <button mat-button (click)="saveItemInfo()"><span translate>Save</span></button>
+    <button mat-button (click)="saveItemInfo()" [disabled]="agendaInfoForm.invalid"><span translate>Save</span></button>
     <button mat-button (click)="onCancelButton()"><span translate>Cancel</span></button>
 </div>
diff --git a/client/src/app/site/agenda/components/item-info-dialog/item-info-dialog.component.ts b/client/src/app/site/agenda/components/item-info-dialog/item-info-dialog.component.ts
index 39e410f66..952862279 100644
--- a/client/src/app/site/agenda/components/item-info-dialog/item-info-dialog.component.ts
+++ b/client/src/app/site/agenda/components/item-info-dialog/item-info-dialog.component.ts
@@ -5,6 +5,7 @@ import { MAT_DIALOG_DATA, MatDialogRef } from '@angular/material/dialog';
 import { ViewItem } from '../../models/view-item';
 import { ItemVisibilityChoices } from 'app/shared/models/agenda/item';
 import { DurationService } from 'app/core/ui-services/duration.service';
+import { durationValidator } from 'app/shared/validators/custom-validators';
 
 /**
  * Dialog component to change agenda item details
@@ -42,7 +43,7 @@ export class ItemInfoDialogComponent {
     ) {
         this.agendaInfoForm = this.formBuilder.group({
             type: [''],
-            durationText: [''],
+            durationText: ['', durationValidator],
             item_number: [''],
             comment: ['']
         });
diff --git a/client/src/app/site/assignments/components/assignment-detail/assignment-detail.component.html b/client/src/app/site/assignments/components/assignment-detail/assignment-detail.component.html
index 3b18effee..ebe9b0a34 100644
--- a/client/src/app/site/assignments/components/assignment-detail/assignment-detail.component.html
+++ b/client/src/app/site/assignments/components/assignment-detail/assignment-detail.component.html
@@ -3,6 +3,7 @@
     mainButtonIcon="edit"
     [nav]="false"
     [editMode]="editAssignment"
+    [isSaveButtonEnabled]="assignmentForm.valid"
     (mainEvent)="setEditMode(!editAssignment)"
     (saveEvent)="saveAssignment()"
 >
@@ -242,16 +243,16 @@
                         formControlName="title"
                         [value]="assignmentCopy.title || ''"
                     />
+                    <mat-error>{{ 'The title is required' | translate }}</mat-error>
                 </mat-form-field>
             </div>
-            <h4>{{ 'Description' | translate }}:</h4>
 
             <!-- description: HTML Editor -->
+            <h4>{{ 'Description' | translate }}:</h4>
             <editor
                 formControlName="description"
                 [init]="tinyMceSettings"
                 *ngIf="assignment && editAssignment"
-                required
             ></editor>
 
             <!-- searchValueSelector: tags -->
@@ -292,8 +293,11 @@
                         matInput
                         placeholder="{{ 'Number of persons to be elected' | translate }}"
                         formControlName="open_posts"
-                        [value]="assignmentCopy.assignment.open_posts || null"
+                        type="number"
+                        required
                     />
+                    <mat-error *ngIf="assignmentForm.get('open_posts').hasError('required')">{{ 'This field is required' | translate }}</mat-error>
+                    <mat-error *ngIf="assignmentForm.get('open_posts').hasError('min')">{{ 'The number has to be greater than "0" ' | translate }}</mat-error>
                 </mat-form-field>
             </div>
             <!-- TODO searchValueSelector: Parent -->
diff --git a/client/src/app/site/assignments/components/assignment-detail/assignment-detail.component.ts b/client/src/app/site/assignments/components/assignment-detail/assignment-detail.component.ts
index 91bdac37a..62b8cb289 100644
--- a/client/src/app/site/assignments/components/assignment-detail/assignment-detail.component.ts
+++ b/client/src/app/site/assignments/components/assignment-detail/assignment-detail.component.ts
@@ -1,6 +1,6 @@
 import { Component, OnInit } from '@angular/core';
-import { FormBuilder, FormGroup } from '@angular/forms';
-import { MatSnackBar } from '@angular/material/snack-bar';
+import { FormBuilder, FormGroup, Validators } from '@angular/forms';
+import { MatSnackBar } from '@angular/material';
 import { Router, ActivatedRoute } from '@angular/router';
 import { Title, DomSanitizer, SafeHtml } from '@angular/platform-browser';
 
@@ -196,10 +196,10 @@ export class AssignmentDetailComponent extends BaseViewComponent implements OnIn
             phase: null,
             tags_id: [],
             attachments_id: [],
-            title: '',
-            description: '',
-            poll_description_default: '',
-            open_posts: 0,
+            title: ['', Validators.required],
+            description: [''],
+            poll_description_default: [''],
+            open_posts: [1, [Validators.required, Validators.min(1)]],
             agenda_create: [''],
             agenda_parent_id: [],
             agenda_type: ['']
diff --git a/client/src/app/site/motions/modules/motion-comment-section/motion-comment-section-list.component.html b/client/src/app/site/motions/modules/motion-comment-section/motion-comment-section-list.component.html
index a59978015..0aa69809f 100644
--- a/client/src/app/site/motions/modules/motion-comment-section/motion-comment-section-list.component.html
+++ b/client/src/app/site/motions/modules/motion-comment-section/motion-comment-section-list.component.html
@@ -13,9 +13,9 @@
             <p>
                 <mat-form-field>
                     <input formControlName="name" matInput placeholder="{{ 'Name' | translate }}" required />
-                    <mat-hint *ngIf="!createForm.controls.name.valid">
+                    <mat-error *ngIf="!createForm.controls.name.valid">
                         <span translate>Required</span>
-                    </mat-hint>
+                    </mat-error>
                 </mat-form-field>
             </p>
             <p>
@@ -39,7 +39,7 @@
         </form>
     </mat-card-content>
     <mat-card-actions>
-        <button mat-button (click)="create()">
+        <button [disabled]="createForm.invalid" mat-button (click)="create()">
             <span translate>Create</span>
         </button>
         <button mat-button (click)="commentSectionToCreate = null">
@@ -62,18 +62,20 @@
                         {{ section.name }}
                     </div>
                     <div class="read">
-                        <mat-icon>visibility</mat-icon>
-                        {{ section.read_groups }}
-                        <ng-container *ngIf="section.read_groups.length === 0">
-                            &ndash;
-                        </ng-container>
+                        <os-icon-container icon="visibility">
+                            {{ section.read_groups }}
+                            <ng-container *ngIf="section.read_groups.length === 0">
+                                &ndash;
+                            </ng-container>
+                        </os-icon-container>
                     </div>
                     <div class="write">
-                        <mat-icon>edit</mat-icon>
-                        {{ section.write_groups }}
-                        <ng-container *ngIf="section.write_groups.length === 0">
-                            &ndash;
-                        </ng-container>
+                        <os-icon-container icon="edit">
+                            {{ section.write_groups }}
+                            <ng-container *ngIf="section.write_groups.length === 0">
+                                &ndash;
+                            </ng-container>
+                        </os-icon-container>
                     </div>
                 </div>
             </mat-panel-title>
@@ -83,9 +85,9 @@
             <p>
                 <mat-form-field>
                     <input formControlName="name" matInput placeholder="{{ 'Name' | translate }}" required />
-                    <mat-hint *ngIf="!updateForm.controls.name.valid">
+                    <mat-error *ngIf="!updateForm.controls.name.valid">
                         <span translate>Required</span>
-                    </mat-hint>
+                    </mat-error>
                 </mat-form-field>
             </p>
             <p>
@@ -128,7 +130,7 @@
             <button *ngIf="editId === section.id" mat-button (click)="editId = null" mat-icon-button>
                 <mat-icon>cancel</mat-icon>
             </button>
-            <button *ngIf="editId === section.id" mat-button (click)="onSaveButton(section)" mat-icon-button>
+            <button *ngIf="editId === section.id" [disabled]="updateForm.invalid" mat-button (click)="onSaveButton(section)" mat-icon-button>
                 <mat-icon>save</mat-icon>
             </button>
             <button mat-button (click)="onDeleteButton(section)" mat-icon-button>
diff --git a/client/src/app/site/motions/modules/motion-detail/components/motion-detail/motion-detail.component.html b/client/src/app/site/motions/modules/motion-detail/components/motion-detail/motion-detail.component.html
index 3ea4bdd03..c202674ab 100644
--- a/client/src/app/site/motions/modules/motion-detail/components/motion-detail/motion-detail.component.html
+++ b/client/src/app/site/motions/modules/motion-detail/components/motion-detail/motion-detail.component.html
@@ -4,6 +4,7 @@
     [prevUrl]="getPrevUrl()"
     [nav]="false"
     [editMode]="editMotion"
+    [isSaveButtonEnabled]="contentForm.valid"
     (mainEvent)="setEditMode(!editMotion)"
     (saveEvent)="saveMotion()"
 >
@@ -631,6 +632,7 @@
                         [value]="motionCopy.title"
                         required
                     />
+                    <mat-error>{{ 'The title is required' | translate }}</mat-error>
                 </mat-form-field>
             </div>
         </div>
@@ -759,7 +761,7 @@
             <div class="motion-text" *ngIf="!editMotion"><div [innerHtml]="sanitizedText(motion.reason)"></div></div>
 
             <!-- The HTML Editor -->
-            <editor formControlName="reason" [init]="tinyMceSettings" *ngIf="editMotion" required></editor>
+            <editor formControlName="reason" [init]="tinyMceSettings" *ngIf="editMotion" [required]="reasonRequired"></editor>
             <div
                 *ngIf="
                     reasonRequired &&
diff --git a/client/src/app/site/motions/modules/motion-workflow/components/workflow-detail/workflow-detail.component.html b/client/src/app/site/motions/modules/motion-workflow/components/workflow-detail/workflow-detail.component.html
index 36bb5d94b..04f9d7712 100644
--- a/client/src/app/site/motions/modules/motion-workflow/components/workflow-detail/workflow-detail.component.html
+++ b/client/src/app/site/motions/modules/motion-workflow/components/workflow-detail/workflow-detail.component.html
@@ -143,6 +143,7 @@
     <div mat-dialog-actions>
         <button
             type="submit"
+            [disabled]="dialogData.value === ''"
             mat-button
             color="primary"
             [mat-dialog-close]="{ action: 'update', value: dialogData.value }"
diff --git a/client/src/app/site/motions/modules/motion-workflow/components/workflow-list/workflow-list.component.html b/client/src/app/site/motions/modules/motion-workflow/components/workflow-list/workflow-list.component.html
index cbb3568b0..0a62cf95d 100644
--- a/client/src/app/site/motions/modules/motion-workflow/components/workflow-list/workflow-list.component.html
+++ b/client/src/app/site/motions/modules/motion-workflow/components/workflow-list/workflow-list.component.html
@@ -36,11 +36,11 @@
     <div mat-dialog-content>
         <p translate>Please enter a name for the new workflow:</p>
         <mat-form-field>
-            <input matInput osAutofocus [(ngModel)]="newWorkflowTitle" />
+            <input matInput osAutofocus [(ngModel)]="newWorkflowTitle" required/>
         </mat-form-field>
     </div>
     <div mat-dialog-actions>
-        <button type="submit" mat-button color="primary" [mat-dialog-close]="newWorkflowTitle">
+        <button type="submit" mat-button color="primary" [disabled]="newWorkflowTitle === ''" [mat-dialog-close]="newWorkflowTitle">
             <span translate>Save</span>
         </button>
         <button type="button" mat-button [mat-dialog-close]="null">
diff --git a/client/src/app/site/tags/components/tag-list/tag-list.component.html b/client/src/app/site/tags/components/tag-list/tag-list.component.html
index ecda87eac..8154989d7 100644
--- a/client/src/app/site/tags/components/tag-list/tag-list.component.html
+++ b/client/src/app/site/tags/components/tag-list/tag-list.component.html
@@ -2,6 +2,7 @@
     [mainButton]="true"
     [nav]="true"
     [editMode]="editTag"
+    [isSaveButtonEnabled]="tagForm.valid"
     (mainEvent)="setEditMode(!editTag)"
     (saveEvent)="saveTag()"
     [multiSelectMode]="isMultiSelect"
diff --git a/client/src/app/site/topics/components/topic-detail/topic-detail.component.html b/client/src/app/site/topics/components/topic-detail/topic-detail.component.html
index 6cbfe98f3..79f8168b9 100644
--- a/client/src/app/site/topics/components/topic-detail/topic-detail.component.html
+++ b/client/src/app/site/topics/components/topic-detail/topic-detail.component.html
@@ -4,6 +4,7 @@
     [nav]="false"
     [goBack]="true"
     [editMode]="editTopic"
+    [isSaveButtonEnabled]="topicForm.valid"
     (mainEvent)="setEditMode(!editTopic)"
     (saveEvent)="saveTopic()"
 >
diff --git a/client/src/app/site/users/components/user-detail/user-detail.component.html b/client/src/app/site/users/components/user-detail/user-detail.component.html
index bd29885a3..454d04f4e 100644
--- a/client/src/app/site/users/components/user-detail/user-detail.component.html
+++ b/client/src/app/site/users/components/user-detail/user-detail.component.html
@@ -4,6 +4,7 @@
     [nav]="false"
     [goBack]="!isAllowed('seeOtherUsers')"
     [editMode]="editUser"
+    [isSaveButtonEnabled]="personalInfoForm.valid"
     (mainEvent)="setEditMode(!editUser)"
     (saveEvent)="saveUser()"
 >