diff --git a/fet2020/authentications/authentications.py b/fet2020/authentications/authentications.py
index aeb1fe07..cd09d144 100644
--- a/fet2020/authentications/authentications.py
+++ b/fet2020/authentications/authentications.py
@@ -27,7 +27,7 @@ def authentication(username, password):
         c = Connection(server, user=userdn, password=password, auto_bind=True)
 
         if not c.extend.standard.who_am_i():
-            logger.info(f"Username '{username}' is not in the list.")
+            logger.info("Username '%s' is not in the list.", username)
             return None
 
         # get member infos from ldap
@@ -43,11 +43,11 @@ def authentication(username, password):
         mail = c.response[0]["attributes"]["mail"][0]
 
     except LDAPBindError as e:
-        logger.info(f"LDAP Bind error from username '{username}'. Error: {e}")
+        logger.info("LDAP Bind error from username '%s'. Error: %s", username, e)
         return None
 
     except Exception as e:
-        logger.info(f"Auth exception from username '{username}'. Error: {e}")
+        logger.info("Auth exception from username '%s'. Error: %s", username, e)
         return None
 
     # get member or if not then create a new member
@@ -57,7 +57,7 @@ def authentication(username, password):
         # set username if not equal
         if member.username != username:
             member.username = username
-            logger.info(f"User '{username}' saved.")
+            logger.info("User '%s' saved.", username)
             member.save()
 
     except Member.DoesNotExist:
@@ -67,10 +67,10 @@ def authentication(username, password):
         member.username = username
         member.nickname = username
         member.mailaccount = mail
-        logger.info(f"Member '{username}' created.")
+        logger.info("Member '%s' created.", username)
         member.save()
 
-    logger.info(f"User '{username}' logged in.")
+    logger.info("User '%s' logged in.", username)
     return username
 
 
@@ -88,7 +88,7 @@ def get_finance_perm(username, password):
         c = Connection(server, user=userdn, password=password, auto_bind=True)
 
         if not c.extend.standard.who_am_i():
-            logger.info(f"Username '{username}' is not in the list.")
+            logger.info("Username '%s' is not in the list.", username)
             return None
 
         # check if member has finance permission
@@ -100,15 +100,15 @@ def get_finance_perm(username, password):
         )
 
         if username in c.response[0]["attributes"]["memberUid"]:
-            logger.info(f"User '{username}' has finance permission.")
+            logger.info("User '%s' has finance permission.", username)
             finance_perm = True
 
     except LDAPBindError as e:
-        logger.info(f"LDAP Bind error from username '{username}'. Error: {e}")
+        logger.info("LDAP Bind error from username '%s'. Error: %s", username, e)
         return None
 
     except Exception as e:
-        logger.info(f"Auth exception from username '{username}'. Error: {e}")
+        logger.info("Auth exception from username '%s'. Error: %s", username, e)
         return None
 
     return finance_perm
@@ -127,8 +127,8 @@ def change_password(username, old_password, new_password):
         return username
 
     except LDAPBindError as e:
-        logger.info(f"LDAP Bind error. Error: {e}")
+        logger.info("LDAP Bind error. Error: %s", e)
     except Exception as e:
-        logger.info(f"Auth change-password exception. Error: {e}")
+        logger.info("Auth change-password exception. Error: %s", e)
 
     return None
diff --git a/fet2020/documents/api.py b/fet2020/documents/api.py
index 2431d43d..6ca99cd2 100644
--- a/fet2020/documents/api.py
+++ b/fet2020/documents/api.py
@@ -62,10 +62,10 @@ def __pad_exists(padID=None):
 
         lists = epc.listPads(groupID=group["groupID"])
         if any(str(padID) in s for s in lists["padIDs"]):
-            logger.info(f"Pad '{padID}' existiert.")
+            logger.info("Pad '%s' existiert.", padID)
             return True
 
-    logger.info(f"Pad '{padID}' existiert nicht.")
+    logger.info("Pad '%s' existiert nicht.", padID)
     return False
 
 
@@ -81,7 +81,7 @@ def create_pad(padID, text="helloworld"):
                 return None
 
             epc.createGroupPad(groupID=group["groupID"], padName=padID, text=text)
-            logger.info(f"neues Pad erzeugt: {padID}")
+            logger.info("neues Pad erzeugt: %s", padID)
 
         return padID
     if __pad_exists(padID=padID):
diff --git a/fet2020/gallery/management/commands/create_thumbs.py b/fet2020/gallery/management/commands/create_thumbs.py
index 2a30573d..d84ea5b5 100644
--- a/fet2020/gallery/management/commands/create_thumbs.py
+++ b/fet2020/gallery/management/commands/create_thumbs.py
@@ -10,7 +10,7 @@ logger = logging.getLogger(__name__)
 class Command(BaseCommand):
     def handle(self, *args, **options):
         for folder in get_folder_list():
-            logger.info(f"Folder '{folder}' in process.")
+            logger.info("Folder '%s' in process.", folder)
             create_thumbs(folder)
 
-        logger.info(f"Command 'create thumbs' ended.")
+        logger.info("Command 'create thumbs' ended.")
diff --git a/fet2020/gallery/utils.py b/fet2020/gallery/utils.py
index b4fc9a3d..4fb64269 100644
--- a/fet2020/gallery/utils.py
+++ b/fet2020/gallery/utils.py
@@ -70,7 +70,7 @@ def create_thumbs(folder_path):
                 continue
 
             image_path = os.path.join(file_path, f)
-            logger.info(f"Edit picture '{f}'.")
+            logger.info("Edit picture '%s'.", f)
 
             with Image.open(str(image_path), "r") as image:
                 if image._getexif() is not None:
@@ -78,4 +78,4 @@ def create_thumbs(folder_path):
 
                 thumb = ImageOps.fit(image, size, Image.ANTIALIAS)
                 thumb.save(thumb_file_path)
-                logger.info(f"Save thumb 'thumb_{f}'.")
+                logger.info("Save thumb 'thumb_%s'.", f)
diff --git a/fet2020/members/models.py b/fet2020/members/models.py
index 07bff4a3..5376e4a5 100644
--- a/fet2020/members/models.py
+++ b/fet2020/members/models.py
@@ -99,7 +99,7 @@ class Member(models.Model):
             try:
                 user = User.objects.get(username=self.username.lower())
             except User.DoesNotExist as e:
-                logger.info("Username does not exist. Error: {}".format(e))
+                logger.info("Username does not exist. Error: %s", e)
             else:
                 user.first_name = self.firstname
                 user.save()
diff --git a/fet2020/members/views.py b/fet2020/members/views.py
index 7bd0b4e3..5803c8bd 100644
--- a/fet2020/members/views.py
+++ b/fet2020/members/views.py
@@ -23,7 +23,7 @@ def jobs(request, slug=None):
     try:
         description = JobGroup.objects.filter(slug=slug).values().first()["description"]
     except Exception:
-        logger.info("Wrong job '{}'".format(slug))
+        logger.info("Wrong job '%s'", slug)
         raise Http404("wrong job")
 
     job_members = JobMember.active_member.get_all(slug=slug).order_by(
@@ -58,7 +58,7 @@ def members(request, role=None):
 def profile(request, member_id=None):
     member = Member.all_members.filter(id=member_id).first()
     if not member:
-        logger.info("Wrong member id '{}'".format(member_id))
+        logger.info("Wrong member id '%s'", member_id)
         raise Http404("no member")
 
     active_jobs = JobMember.members.get_active_jobs(member_id)
diff --git a/fet2020/posts/cronjobs.py b/fet2020/posts/cronjobs.py
index a7f1ebc9..15d628d8 100644
--- a/fet2020/posts/cronjobs.py
+++ b/fet2020/posts/cronjobs.py
@@ -18,5 +18,5 @@ def check_to_send_agenda_mail():
     next_meeting = FetMeeting.objects.filter(event_start__date=agenda_date).first()
 
     if next_meeting and next_meeting.has_agenda:
-        logger.info(f"Agenda für die {next_meeting.slug} soll gesendet werden.")
+        logger.info("Agenda für die %s soll gesendet werden.", next_meeting.slug)
         send_agenda_mail(next_meeting)
diff --git a/fet2020/posts/mails.py b/fet2020/posts/mails.py
index ce40c301..2ae9e5dc 100644
--- a/fet2020/posts/mails.py
+++ b/fet2020/posts/mails.py
@@ -32,6 +32,6 @@ def send_agenda_mail(meeting):
         from_email="service@fet.at",
         recipient_list=["patrick@fet.at"],
     ):
-        logger.info(f"Mail für die Agenda {meeting.slug} wurde gesendet.")
+        logger.info("Mail für die Agenda %s wurde gesendet.", meeting.slug)
     else:
-        logger.info(f"Mail für die Agenda {meeting.slug} wurde nicht gesendet.")
+        logger.info("Mail für die Agenda %s wurde nicht gesendet.", meeting.slug)
diff --git a/fet2020/posts/models.py b/fet2020/posts/models.py
index dc0f327c..73c8b031 100644
--- a/fet2020/posts/models.py
+++ b/fet2020/posts/models.py
@@ -173,7 +173,9 @@ class Post(models.Model):
 
         set_pad_html(self.agenda_key, value)
 
-        request_logger.info(f"set etherpad for post {self.slug} id: {self.agenda_key}")
+        request_logger.info(
+            "set etherpad for post %s id: %s", self.slug, self.agenda_key
+        )
         return value
 
     @protocol_html.setter
@@ -186,7 +188,7 @@ class Post(models.Model):
         set_pad_html(self.protocol_key, value)
 
         request_logger.info(
-            f"set etherpad for post {self.slug} id: {self.protocol_key}"
+            "set etherpad for post %s id: %s", self.slug, self.protocol_key
         )
         return value