Not turning on the next day after battery replacement

Hi, so I had this iPhone 6s laying around, completely dead. Replaced the charging port on it and the battery, then it turned on. Let it charge, used it for a bit, but noticed it got quite hot around the camera, so I turned it off for the night. Now the next day when I try to turn it on, it's completely dead yet again, Power + Home Button does nothing, computer doesn't see it. So I'm guessing there was something else that killed the previous battery. Any ideas?

Not much hope, but I'll try to revive this thread. I got this battery charger from Aliexpress and it revived the phone. It isn't the front this heating up, but the back. I disconnected the back camera and it doesn't seem to heat up as much. But the main chip inside is kind of hot to the touch, but it's while charging, so I guess it's normal? But the next problem I have is that Wi-Fi is really buggy, 90% of the time it won't connect to my Galaxy S21+ hotspot and 99% of the time doesn't detect my universities network. So I'm guessing the logic board is as good as dead at this point? As far as I know this phone just was put aside, wasn't used for a few months and just died.