Hey I had the same problem but what
I did was 1)clean everything at the bottom of the iPhone like the speakers and charger slot also the earphone slot at the top with a cotton stick and alcohol 2) trun off phone 3)
Take a hair dryer and dry the parts you cleaned 4)leave phone off for 5-3 mins 5) put on your phone and open it and try the buttons
-this worked for me try it and see if it works for you