Hey Torsten,
The reason that the "mini registration" isn't appearing for you is because all of the custom fields in your "Registered" profile type is disabled on the mini registration view.
To configure which custom fields should appear on the mini registration,
1. Go to Profile Types
2. Click on the profile type
3. Click on the custom fields tab
4. Click on the field that you want to configure
5. Click on the "View" tab for the field settings.
6. Ensure that the "Enable in mini registrations" is enabled.
I have configured some fields for you and it is displaying the mini registration now at
https://www.schwedenhaus.ag/community