Installtion was perfect - nearly perfect - only blanc site

hello,
after Installation I can see only the blanc side - no css…:thinking:
If I change the theme nothing happens…
I tried this with Omeka Classic and Omeka S…

Is this a host Problem?

Do I have to Change some settings in the Code?

… and I can upload files - but cant Display them…

https://muesum.eu/

Any ideas?

greetings from Germany

Nafets