Chosen Solution
Earlier this morning my screwdriver slipped when screwing in the top left screw ( for the plate that holds all the display/digitizer/home button cables). I see no physical damage, but the phone has been in an bootloop ever scince. Even with the old screen. It slipped over the chips on the left of that nut. Any possible fixes? Or should I just send it to Apple for repair ( out of warranty, they said it would cost maximum 390 euros).
There are some components right next to the top-left screw mount. You probably did some damage to that part of the board. I would use some magnification and carefully inspect that part of the board to see if there are any dislodged or missing components. This could be a relatively simple fix for a micro-solderer, certainly less expensive than replacing your phone with a refurbished device. I would also like to to add that boot looping can be caused by Long-Screw Damage. That is when you put the screws back incorrectly (a long one where a short one should go). I would follow this guide (step 12) and double check the screw lengths and placement.
