Battery drained and the iPhone overheated then stopped responding

Hi

I had an issue with my iPhone a few weeks ago which happened while I was texting with my iPhone then suddenly the device overheated from one particular spot which was from the backside of the phone under the camera’s lens within half an inch to be specific. I noticed that the battery percentage is dropping down fast so I immediately turned the phone off, the phone kept heating while it’s turned off I placed it under the AC to cool it down then I tried to switch it on and the phone has drained all the battery, I charged my phone then I turned it on again and it worked normally for a few seconds and after that, it overheated again and the same thing happened to the battery as it drained out rapidly but this time it never turned back on. I tried to switch the phone on, connect the phone to my mac, did all the push and hold buttons methods on the web and the phone refuses to turn on, or give any sign that it's a life.

I lift the phone for a few weeks and now I’m thinking of fixing my iPhone but what I'm concerned about is what are the parts that need replacement.

I hope if someone can make sense of what happened with me and tell me what are the parts that I need to buy, and perhaps what possibly could cause this to happen as my iPhone was always in a tank case (a heavy-duty one), Also I don’t remember dropping my phone or exposing it to any liquid in the past days before that incident occurred.