It's a total mess up, impossible to even try to figure out what you have done.
And what it should look like
If you want to know what it should look like see https://ergo-film.info/ ( resize your browser to mobile size.)
Like that I would like partly the desktop size...

That's good then that you found the tutorial so now you can follow along again and create it again

thanks for your help

When you have re-created that menu, then perhaps you can post it as a component BEFORE TRYING to change the action at the higher breakpoint, so that we can try to help, from the start. with a clean slate so to speak.

There are other menu's available that are much simpler and easier to get the effect you want, even some that are ready made components.Just a simple matter of styling it as to how you want.