Hey Andreas,
That is normal. The Navigation Inline will not automatically change to a mobile nav like the Classic (X) Header. In Pro, you need to hide the Navigation Inline element using the Hide During Breakpoints feature and show a Navigation Collapsed or a Navigation Layered (only differs in method to open the submenu) element in its place. The Hide During Breakpoints feature is available in all non-Classic elements.
Now that you know this setup, one big advantage of Pro is you can set a different screen size to show a collapsed menu. An example of that is collapsing a long menu earlier.
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Though this mobile nav menu is still part of your header problem, it is no longer connected to the original problem which is “Content being hidden behind header”. It’s okay if I answer the thread. But, if another support staff takes this thread, s/he might get confused as this is a very long thread.
It’s strongly recommended to open a separate thread for issues that are not connected because mixing topics in one thread often lead to confusion and results to delayed response.
Hope that helps.