iPhone screen looks like an X-ray
Why does my wife’s iPhone 6s Plus all of a sudden look like an X-ray?
iPhone 6s Plus
Try to do a force restart -> Force restart iPhone – Apple Support (UK)
If it doesn't help / if the problem persists, visit an Apple Store or an Apple Authorized Reseller in your region for assistance to diagnose the problem.
And they could offer a possible solution.
(perhaps) You will first have to make an appointment due to the pandemic.
See: Contact Apple for support and service
Contact Apple for support and service - Apple Support
Make a back up before you visit an Apple Store or an Apple Authorized Reseller, see -> How to back up your iPhone, iPad, and iPod touch
How to back up your iPhone, iPad, and iPod touch - Apple Support