iPhone 5C repair questions

I don't know really what is wrong with my 5C, the screen used to work, and then the corner of the screen popped out, and I fixed it by popping it back in, but then the phone started glitching, and now won't even turn on, the whole screen can pop out now, (Because I took the screws out), but I'm not 100% if its my LCD Screen thats broken, or something else in my phone, what should I check/ look out for?