iPhone 6 screen goes black when waking up from sleep

Hello,

I got my screen replaced and now the screen sometimes goes black when it wakes up from sleep. It also happens when turning on and off airplane mode. The only fix is spamming the power button until the screen shows. It is still on because I can still hear the charging noise when plugged in. When I am using it, it does not go black. Also, the camera and flash also do not work. It says "iPhone needs to cool down before you can you flash" even when the phone is not hot. The rear camera is black but the front camera works. Everything else works properly.