Why is my phone getting hot?

My phone would not completely charge, would get to 28% then stop. I would turn phone on then battery would drain within a few minutes. Then next time I tried to charge it, it would say 0% and would charge no further. I replaced the charging port and it charged all the way up but then would not turn on. So I replaced the power button ribbon cable. It turned on and everything started to load but the phone started getting very very hot. So I took battery out.

What did I do wrong?? It is the original battery. Everything else is original too. Just replaced charging port and power button ribbon cable. Bought both parts from a reputable person on ebay.

PLz help.

Thanks. Misty