I your demo, the page-list header/navigation is hidden, while I open any page.
It appears only while hovering over with the mouse. How can I achieve this on my page?
Attached files: Hide_Navi.PNG
The auto-hide menu works perfectly in a test installation that I just uploaded on my site, even in the customizer live preview (w/o Werkstatt being the active theme).
As far as I can see, you are using an up-to-date version of the theme and the WP stack. You might want to try to temporarily deactivate all of your plug-ins and see if the problem persists.
Best wishes, Thomas
Thank you Thomas, it works now