At first, when opening your two files, I had to scratch my head a bit before I got to work, though. I think you are using much too much grid, especially in the menu links. No need for grid there IMO.
It seems to work now. What I did was separating the two menu bits, the mobile from the desktop one. You'll see that in the code. Then, because the mobile nav is positioned fixed, I had to add some top padding to the nav-desktop-all container, to prevent the contents from sliding up behind the mobile nav. Also, I gave the desktop menu the same width as you had provided for it in the grid.
I popped the menu into the grid-parent, and I think it will work also with the site.
I had a look at your current site, BTW, and recognized Otto Waalkes and Karl Dall from the time I was living in Berlin and happened to see them in various pubs where they were performing. Happy memories for me, sitting in the audience listening to them, + Hannes Wader, Schobert und Black, Reinhard Mey.... Oh yeah, auch Ich hab noch einen Koffer in Berlin
https://www.dropbox.com/s/9udyo3uc0bazc … r.rsd?dl=0
Inger, Norway
My work in progress:
Components for Site Designer and the HTML Editor: https://mock-up.coffeecup.com