My iPhone 14 Pro max screen is frozen since yesterday

Not sure what steps you followed, but you should do a Force Restart. This may take a couple of attempts to get the speed and sequence of the key presses correct and the last step of holding the side button until the Apple Logo appears could take up to 20 seconds. Ignore anything else on the screen during that time.

Force restart iPhone - Apple Support

We don't know what steps you might have tried.

Perform a Forced Restart on the phone. Follow the instructions very carefully, as this is a bit tricky. You may need to repeat this several times.

You have to keep holding the Side Button when you see the "Slide to power off" screen for another 10-15 seconds until the Apple logo appears. Then....you can release the Side Button and the phone will restart.

Force restart iPhone - Apple Support

There are only 2 possible results when you perform a Forced Restart:

1) The phone returns to normal operation

However, if the screen is still frozen.....

2) There is a hardware problem with the phone that will need attention at the Apple Store (make an appointment) or take the phone to an authorized Apple Service shop.

You can find a list of authorized service shops in your area using the link just below:

Find Locations