Mac won't start?

Question

macOS

Hello. After updating Mac OS, I enter the user password and get a screen that says "restarted because of a problem mac"
There is no backup of the system.
Only rearranging the system will help? Or are there other options?
And the second question. Is it possible to rearrange while keeping all the data? Although in fact only the folder with the pictures is important.

Answer 1

Is it possible to rearrange while keeping all the data?

possible: just do not format the drive during installation.
you can also boot into recovery mode and merge the necessary data to an external drive.

Answer 2

Of course available. Roll the system over and that's it. When you update the OS, all files and all software remain in place.