diff --git a/openslides/agenda/models.py b/openslides/agenda/models.py
index 88b4d9579..12b921a67 100644
--- a/openslides/agenda/models.py
+++ b/openslides/agenda/models.py
@@ -284,20 +284,6 @@ class Item(RESTModelMixin, models.Model):
     def __str__(self):
         return self.title
 
-    def delete(self, with_children=False):
-        """
-        Delete the Item.
-
-        If with_children is True, all children of the item will be deleted as
-        well. If with_children is False, all children will be children of the
-        parent of the item.
-        """
-        if not with_children:
-            for child in self.children.all():
-                child.parent = self.parent
-                child.save()
-        super().delete()
-
     @property
     def title(self):
         """
diff --git a/openslides/agenda/projector.py b/openslides/agenda/projector.py
index b318ba5d6..e8ce31f5d 100644
--- a/openslides/agenda/projector.py
+++ b/openslides/agenda/projector.py
@@ -62,7 +62,7 @@ class ListOfSpeakersSlide(ProjectorElement):
                     yield speaker.user
 
     def get_collection_elements_required_for_this(self, collection_element, config_entry):
-        output = super().get_collections_required_for_this(collection_element, config_entry)
+        output = super().get_collection_elements_required_for_this(collection_element, config_entry)
         # Full update if item changes because then we may have new
         # candidates and therefor need new users.
         if collection_element == CollectionElement.from_values(Item.get_collection_string(), config_entry.get('id')):
diff --git a/openslides/assignments/models.py b/openslides/assignments/models.py
index 98e63d3e4..40fe85a00 100644
--- a/openslides/assignments/models.py
+++ b/openslides/assignments/models.py
@@ -16,6 +16,7 @@ from openslides.poll.models import (
     CollectDefaultVotesMixin,
     PublishPollMixin,
 )
+from openslides.utils.autoupdate import inform_changed_data
 from openslides.utils.exceptions import OpenSlidesError
 from openslides.utils.models import RESTModelMixin
 from openslides.utils.search import user_name_helper
@@ -209,6 +210,7 @@ class Assignment(RESTModelMixin, models.Model):
         Delete the connection from the assignment to the user.
         """
         self.assignment_related_users.filter(user=user).delete()
+        inform_changed_data(self)
 
     def set_phase(self, phase):
         """
diff --git a/openslides/core/models.py b/openslides/core/models.py
index 926bc3073..bdb6d0c40 100644
--- a/openslides/core/models.py
+++ b/openslides/core/models.py
@@ -15,6 +15,19 @@ from .access_permissions import (
 from .exceptions import ProjectorException
 
 
+class ProjectorManager(models.Manager):
+    """
+    Customized model manager to support our get_full_queryset method.
+    """
+    def get_full_queryset(self):
+        """
+        Returns the normal queryset with all projectors. In the background
+        projector defaults are prefetched from the database.
+        """
+        return self.get_queryset().prefetch_related(
+            'projectiondefaults')
+
+
 class Projector(RESTModelMixin, models.Model):
     """
     Model for all projectors. At the moment we support only one projector,
@@ -57,6 +70,8 @@ class Projector(RESTModelMixin, models.Model):
     """
     access_permissions = ProjectorAccessPermissions()
 
+    objects = ProjectorManager()
+
     config = JSONField()
 
     scale = models.IntegerField(default=0)
diff --git a/openslides/core/signals.py b/openslides/core/signals.py
index 92609c323..f2667ca21 100644
--- a/openslides/core/signals.py
+++ b/openslides/core/signals.py
@@ -20,8 +20,7 @@ def delete_django_app_permissions(sender, **kwargs):
         Q(app_label='auth') |
         Q(app_label='contenttypes') |
         Q(app_label='sessions'))
-    for permission in Permission.objects.filter(content_type__in=contenttypes):
-        permission.delete()
+    Permission.objects.filter(content_type__in=contenttypes).delete()
 
 
 def create_builtin_projection_defaults(**kwargs):
diff --git a/tests/integration/core/test_viewset.py b/tests/integration/core/test_viewset.py
index 926bfa39b..c1a803fa6 100644
--- a/tests/integration/core/test_viewset.py
+++ b/tests/integration/core/test_viewset.py
@@ -26,9 +26,10 @@ class TestProjectorDBQueries(TestCase):
         Tests that only the following db queries are done:
         * 5 requests to get the session an the request user with its permissions,
         * 2 requests to get the list of all projectors,
+        * 1 request to get the list of the projector defaults.
         """
         self.client.force_login(User.objects.get(pk=1))
-        with self.assertNumQueries(7):
+        with self.assertNumQueries(8):
             self.client.get(reverse('projector-list'))
 
     def test_anonymous(self):
@@ -36,12 +37,13 @@ class TestProjectorDBQueries(TestCase):
         Tests that only the following db queries are done:
         * 2 requests to get the permission for anonymous (config and permissions)
         * 2 requests to get the list of all projectors,
+        * 1 request to get the list of the projector defaults and
 
         * 11 requests for permissions.
 
         TODO: The last 11 requests are a bug.
         """
-        with self.assertNumQueries(15):
+        with self.assertNumQueries(16):
             self.client.get(reverse('projector-list'))