Hamburger menu opacity/priority

My very amateurish site,, uses horizontal menus in wide-desktop PC mode but the hamburger menu in tablet and portrait smartphone modes. However, when you click or press on the hamburger menu, it always gets lost in the elements of whatever the main page below the header is: text or image or whatever is situated at the top. How do I force the list of hamburger menu items to appear on top of the page elements? (The problem is most apparent in portrait smartphone mode.)

Hi mjp,
Click and hold shift the title and image and in the arrange tab “send to back”
That should work.

Japanese History & Material Culture