@arminunruh
where, how, what can i enter, that the mobile-menue hides ?

perhaps, a simple way to implement it now would be to make the "start page" the footer page in the respective post - or to make a kind of portfolio page with the infinite scroll character and make it the footer page similar to this:
https://rbfk.de/ausstellungskatalog/

Hi
here are some pages we made with Lay... it's a perfect tool to implement ideas and designs.
Keep going

https://bruecke.modernegalerie.org/

https://alexandergegia.com/

https://rbfk.de/

All Best