diff --git a/rc_hip/rc_hip/settings.py b/rc_hip/rc_hip/settings.py
index 393dc44..5f216bf 100644
--- a/rc_hip/rc_hip/settings.py
+++ b/rc_hip/rc_hip/settings.py
@@ -185,3 +185,22 @@ if DEBUG:
 else:
     LOGIN_REDIRECT_URL = "https://anmeldung.repaircafe-hilpoltstein.de/"
     LOGOUT_REDIRECT_URL = "https://anmeldung.repaircafe-hilpoltstein.de/"
+
+
+LOG_LEVEL = "INFO"
+if DEBUG:
+    LOG_LEVEL = "DEBUG"
+
+LOGGING = {
+    "version": 1,
+    "disable_existing_loggers": False,
+    "handlers": {
+        "console": {
+            "class": "logging.StreamHandler",
+        },
+    },
+    "root": {
+        "handlers": ["console"],
+        "level": LOG_LEVEL,
+    },
+}
diff --git a/rc_hip/repapp/backends.py b/rc_hip/repapp/backends.py
index 130f735..ac8e454 100644
--- a/rc_hip/repapp/backends.py
+++ b/rc_hip/repapp/backends.py
@@ -2,11 +2,14 @@
 Authentication backends for RepApp.
 """
 import unicodedata
+import logging
 from django.contrib.auth import get_user_model
 from django.contrib.auth.backends import ModelBackend
 from mozilla_django_oidc.auth import OIDCAuthenticationBackend
 from .models import OneTimeLogin, Organisator, Reparateur
 
+logger = logging.getLogger(__name__)
+
 
 def generate_username(email):
     # Using Python 3 and Django 1.11+, usernames can contain alphanumeric
@@ -71,19 +74,31 @@ class KeycloakOIDCAB(OIDCAuthenticationBackend):
 
     def create_user(self, claims):
         user = super(KeycloakOIDCAB, self).create_user(claims)
+        logger.debug(f'Create user {user.email}')
 
-        user.username = claims.get(
-            'preferred_username', generate_username(user.email))
-        user.save()
+        try:
+            user.username = claims.get(
+                'preferred_username', generate_username(user.email))
+            user.save()
+        except Exception as exception:
+            logger.error(exception)
+            user.username = generate_username(user.email)
+            user.save()
+
+        logger.debug(f'Updated username {user.username}')
 
         create_repapp_user(user)
 
         return user
 
     def update_user(self, user, claims):
-        user.username = claims.get(
-            'preferred_username', generate_username(user.email))
-        user.save()
+        logger.debug(f'Update user {user.email} ({user.username})')
+        try:
+            user.username = claims.get(
+                'preferred_username', generate_username(user.email))
+            user.save()
+        except Exception as exception:
+            logger.error(exception)
 
         create_repapp_user(user)
 
diff --git a/rc_hip/repapp/views.py b/rc_hip/repapp/views.py
index 5704c7f..4bc85f4 100644
--- a/rc_hip/repapp/views.py
+++ b/rc_hip/repapp/views.py
@@ -271,8 +271,15 @@ class RegisterGuestFormView(generic.edit.FormView):
         if not CustomUser.objects.filter(email=mail).exists():
             password = ''.join(random.choice(string.ascii_letters)
                                for i in range(10))
+
+            username = name
+            i = 1
+            while CustomUser.objects.filter(username=username).first():
+                username = f'{name}{i}'
+                i = i + 1
+
             user = CustomUser.objects.create_user(
-                username=name,
+                username=username,
                 email=mail,
             )
             user.set_password(password)