Hi mushofromyerevan,
Using diagnostics in iOS, we’ve detected an issue with your TrueDepth camera that might cause it to not function as expected. This won’t prevent you from using your iPhone X, but you won’t be able to use Face ID, Animoji, and some other features using the front camera until your iPhone X is serviced.If Face ID is disabled on your iPhone X - Apple Support.
or Take your iPhone to an Apple Authorized Service Provider or make a Genius Bar reservation at the Apple Store. You can also contact Apple Support.