Currently your background image is added in the nav bar where menu is located. On mobile devices a standard desktop menu is hidden and mobile menu loads, so background image can’t be visible.
If you want to show it on mobile you have to set background image for header and not for nav bar (with the code I added you in the previous post).
To remove it from footer you need remove the code:
Please note background image can’t be shown on mobile devices as now it’s added in the menu section and on mobiles standard menu is hidden, so the background image is hidden too.
