No service and “overheating”?

One of my family members had thrown their iPhone 12 Pro Max on the floor and it had shattered the back glass. It was definitely worse than that since soon after the phone said it was overheating but it was cool, and it said that the phone had no service. I’m pretty sure the impact was around the camera. I’m not really looking for any help repairing. I just want to know what part is having issues, and if my family could repair it or would it be best to completely buy a new phone. Thank you.