camera and cellular not working after dropping the phone

My iPhone 6s has dropped. Since then, the back camera didn't work anymore. After opening it, I noticed the camera bracket was a bit blue - probably caused by heat. So I assumed there was a short circuit.

I replaced the camera but it still didn't work. Also, the cellular wasn't working any longer.

Then I replaced the Lightning connector flex cable, assuming that caused the cellular problem. But it didn't.

So I take it the problem is caused by something else, but I have no clue. Could it be the motherboard?

Many thanks.