Is my phones hardware failing or is it just the touchscreen failing?

Well a couple of months ago, My phone[redmi 4/mi 4] started showing signs on a bulging battery, the phone has a metal back which due to the bulging, started to strain the screen, even at minor usage, the screen kept bending and I chose to put in a new battery, once the new battery was in, The bottom part of my touch screen started to show two issues. it either dostn’t let me touch that part of the screen and get no touch response or it just kept rapidly clicking at the bottom whenever i touched any part on the screen, causing unwanted actions which frankly gets on my nerves, it has been sometime and now I have used some application i found at the play-store to block any touch in that segment. the probelm I need answered is what could be broken, Could it be the screen, the digitizer or both or worse, the motherboard itslef, I don’t understand what part of it I should change, please help me out.