Phone reset after battery replacement

Hello,

Since this is my first iPhone repair, I messed up a few things: the power button flex cable broke, the wireless charger flex cable broke, and I broke the proximity sensor on the screen. Right now, when I put the battery in, the screen turns on and the phone starts up without any problems, but when I start using it, it overheats within 5 minutes and the phone restarts itself. I've left the phone on Always On Display, and it's been running for an hour, but as soon as I start using it, it shuts down within 5 minutes. I tried two separate batteries I bought from Amazon. The first battery stayed at 1% after a few reboots, but this battery remembers the percentage and is a good battery. My question is, if I buy the flex cables as separate parts and install them, will the problem be fixed? Or am I just wasting money?
Thanks!

I want to add that the part that heats up the most is the screen flex that transmits the image to the phone. The end of the flex connected to the motherboard gets very hot.