@Lena-str, @nicolas36 Things I would try, in this order (go to the next step, if the former did not solve the issue):
- Do the Touchscreen Test. If the touchscreen works in testing mode then there is an issue with the software and you need to reinstall FP OS.
- Disassemble your phone and reassemble it again. Check every connector again. I have experienced problems after a display assembly because of loosely connected cables.
- Get a new display or send your phone in for repairs.