Can you help me to open Face ID ?

Should you have been using the reference article above your thread in this page

there are details within it; directs you to authorized service provider or Apple, to

have the iPhone unit inspected and serviced.

If you noticed an "Alert, that said "Face ID has been disabled", the situation is clear.

And if the Apple diagnostics ran, you may or not have been party to that action.

• If an alert says Face ID has been disabled on your iPhone or iPad Pro - Apple Support

The matter involves hardware, firmware or software issue; & needs to be serviced.

As the TrueDepth camera and other technologies are off-limits to user tampering

and those would need to be addressed at an AASP or official Apple repair center.

• Genius Bar Reservation and Apple Support Options - Apple

//www.apple.com/retail/geniusbar/

An store Genius at Apple retail could direct your iPhone to have it serviced, off-site.

There's more than a few options linked to the above site page. Hardware & software.

• iPhone Repair - Official Apple Support

//support.apple.com/iphone/repair/service

Through contacting Apple online or by phone, etc; in some regions they can have

an authorized service handle the matter; and have your repaired phone returned.