rear camera and face id on iphone x doesn’t work

These are the support guides for your issues:

Get help with the camera on your iPhone, iPad, or iPod touch - Apple Support

and

Use Face ID on iPhone X - Apple Support

or

Get help with Face ID on your iPhone X - Apple Support

If you get no help, since your iPhone is still on warranty, I would have it checked at your most convenient Apple Store or Authorized Service Provider:

Apple - Find Locations - Location Selector

Regards

Giulio

Hi

Go to settings down to face I'd delete face I'd Then set back up again.

If you still have a problem make an appointment at Apple store or authorised apple repairer.

Cheers

Brian 🇬-1F1E7;