Insert going under everyting

Try selecting all and M to merge by distance just in case you have doubles. After that you can go into face mode and just delete that face there so what's down below isn't occluded by it.

That means you have one huge face. You can delete it and start creating new faces with F by selecting a couple of vertices at a time. Kinda hard to explain, but it's just as JL is doing in the video.

HI Ionut IIonutTT ,

That Face is covering the Buttons. If you pull them down, those Buttons will still be covered by that large Face.

If you are Filling something (with F), you must be careful what you have Selected: