iPhone 7 Diagnostics Problem (apple logo)

Iphone 7 is stuck on diagnostics screen

Hi, my iphone 7 is stuck on the diagnostics screen and the only option given is to exit diagnostics. When I touch that blue 'exit diagnostics' tab my phone then goes to the white screen with the black apple logo. My phone is full and hasn't been backed up in a while. I was trying to delete photos and videos to make space but it would not allow me to delete anything so I powered it off but then I got the white screen with the black apple logo. I was then able to get to diagnosics but am now stuck on that. And on my MacBook it says when trying to connect it “Value is missing”I really don't want to lose any of my stuff. HELP!!!

[Image Edited by Moderator to Remove Personal Information]