Face id and brightness issue.

Good day.

my phone was at 5 percent battery when I noticed the error that face id doesn't work, I tried to restart the phone and after that it went into the boot loop until it turned off. When I got home I put it on the charger and turned on the phone and then 5 minutes of bootloop managed to boot the system. It is not possible to use Face ID and the brightness of the screen is reduced to a minimum without the possibility to adjust it. I tried hard reset update, but every time it turned off, it would go into bootloop and only come back to life after some time (sometimes 5 minutes, sometimes several hours). and the update would not be installed. Have you had any experience with this problem and what is the cause?