layout/profile theme on mobile

why does my layout on the mobile site/app look the way it does? like there's still some stuff left but for the most part it looks mostly default but on desktop it looks fine and somewhat complete. i'm not really an expert on site building/coding, so if it's a complicated answer please explain thoroughly

and on the app, my code is still there, are they not able to "convert" it so everything is the same (just rearranged to fit the phone screen)?

i can provide my whole code thing, just ask. thank you