David,
header and menu are sticky now, but there is one strange thing: On pages built with elementor the contents scroll in front of the header and the menu (cf. start page). Whereas on pages built with the the classic wordpress editor the scrolling is correct, i.e. header and menu stay in the foreground, contents disappear behind when scrolling (cf. “Datenschutz”; “Impressum”).
I checked the difference with another test page using elementor, the result is the same.
Currently I have deactivated the css code due to the issue.
Gerhard