Phone is barely working

Hi, I've got my Sony Xperia xz premium, which has pretty heavy cosmetic damage on the back of the phone. These are the things that currently don't work on my phone : volume down button, front camera, rear camera, torch/flashlight, also when calling someone the screen goes dark and stays like that until the call is ended, perhaps problem with the sensor. I really like this phone and I don't want to just throw it away, so therefore I'm looking for someone who could fix, the repair shops charge too much money.