Menu sizing for iPad Customization

I have a menu on a website currently that plays terribly on iPad. The customer is adamant about not changing the menu, which I get. Forgive my lack of know-how. But I’m wanting to figure out a way to say " If screen size = XX" "then do This to the menu. Any help would be appreciated. I know on editor X this is very easy to do.
Screens are below


DESKTOP VERSION


DESKTOP VERSION ON IPAD