Hi!
It seems to me that you are experiencing an issue with your OLED display on your iPhone X.
I'm very sorry for the inconvenience. It's quite unfortunate that you are having this issue, but you can try to restart your iPhone.
You can do this by following these steps:
- Press and hold the Side button and either volume button until the slider appears.
- Drag the slider to turn your device completely off.
- After your device turns off (spinning wheel disappears), press and hold the Side button again until you see the Apple logo.
If this issue does persist, I urge you to contact Apple Support and they may be able to help you further or even replace your iPhone if it is still within the warranty period.
https://getsupport.apple.com/?caller=psp&PRKEYS=PL133