Thanks for your reply, but that´s not exactly what I mean.
When you have a relatively large amount of menu items and you open the menu (mobile / bigger screen is set to ‘hamburger’ menu, second menu option) a part of the menu will be off screen. When you scroll down the page behind it will scroll, but not the menu itself. It does not matter which header setting you have, because the mobile menu is always the same.
Is there any way (except from restricting the number of menu items) to make the menu behave differently?