Hello filippos129,
Welcome to Apple Support Communities!
We want to make sure the screen is working perfectly on your iPhone.
Try these steps to help resolve an issue related to the display:
"If the screen isn't working on your iPhone or iPad
You might need to set up service for your device.
If your screen is too sensitive or responds intermittently to touch
- Restart your iPhone or iPad.
- Make sure that your screen is clean and free of any debris or water.
- Disconnect any Lightning or USB-C accessories. If your screen works after removing an accessory, try using a different outlet, cable, or charger.
- Remove any cases or screen protectors.
Contact Apple Support
If your screen still isn't working, you might need to set up service for your device. Contact Apple Support."
This Apple Support page has the full details: If the screen isn't working on your iPhone or iPad - Apple Support
Use the link to reach Apple Support directly if it's hardware related so they can further investigate your best options.
We hope this helps to resolve the issue causing the line issue.
Cheers!