How do I know my dead phone needs a battery or a screen

I opened the device for cleaning purpose and it was working when I tried it after opening the device, then I turned it off and cleaned the edges of the battery (I didn't touch the right side of the battery) I encountered some

Problems when installing the screen and after that I tried to start the device not working, so is the problem from the screen battery? (I didn't touch anything else, the left side of the battery and the screen only returned) + When charging the phone, I feel, but the electricity is in the back, as usual