Hello StephTech77,
Have you tried Force Restarting your phone? This would help if the device is freezing, although it sounds like your issue is display related, but this step won't hurt anything. -> Force restart iPhone - Apple Support
It sounds as if you may have a display that needs to be replaced. An Apple Store or Authorized Repair Facility can run display diagnostics to confirm. I would use any of the following links to create an appointment at your nearest store of choice.
Also, before you go, make sure you have a backup of your device.
Backup -> How to back up your iPhone, iPad, and iPod touch - Apple Support
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