My phone is overheating, help

Today my phone randomly restarted, I started it again and put it in my bag. After 30-40 minutes i took it back and it was super hot and had to remove battery. After it cooled off i turned it on again and it started overheating when nothing was on. Right now I got back home at started charging it from 0% battery but it again started to get warmer.

Update 1 : Now I see that not the battery is overheating, its the phone itself, above the battery pit and I don't even have mobile connection for...

My phone is overheating, help

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