resolve issues with new features

frontend/src/components/shared/NotificationBell.tsx

@@ -138,6 +138,15 @@ const NotificationBell: React.FC = () => {
     }
   };
 
+  const handleDeleteAllRead = async () => {
+    try {
+      await notificationsApi.deleteAllRead();
+      setNotifications((prev) => prev.filter((n) => !n.gelesen));
+    } catch {
+      // non-critical
+    }
+  };
+
   const open = Boolean(anchorEl);
   const hasUnread = unreadCount > 0;
 
@@ -169,11 +178,18 @@ const NotificationBell: React.FC = () => {
           <Typography variant="subtitle1" fontWeight={600}>
             Benachrichtigungen
           </Typography>
-          {unreadCount > 0 && (
-            <Button size="small" onClick={handleMarkAllRead} sx={{ fontSize: '0.75rem' }}>
-              Alle als gelesen markieren
-            </Button>
-          )}
+          <Box sx={{ display: 'flex', gap: 0.5 }}>
+            {notifications.some((n) => n.gelesen) && (
+              <Button size="small" onClick={handleDeleteAllRead} sx={{ fontSize: '0.75rem' }}>
+                Gelesene löschen
+              </Button>
+            )}
+            {unreadCount > 0 && (
+              <Button size="small" onClick={handleMarkAllRead} sx={{ fontSize: '0.75rem' }}>
+                Alle als gelesen markieren
+              </Button>
+            )}
+          </Box>
         </Box>
         <Divider />