Hi Maximilian118,
That’s quite a few photos!
How do you think we can figure it out without access to your server, or information from you?
When you started writing your story, there was a helpful text in the edit window, with a default template that asks you for details of your setup.
In general, you’d be looking to log in via SSH and run occ files:scan, which makes Nextcloud aware of your newly added photos.