Reinstalling macOS does not have to erase your user data. The only time that should happen is if you choose to delete, erase, format or partition your startup drive.
If you restart your Mac in Recovery mode and simply select Reinstall macOS from the macOS Utilities window, the OS should be reinstalled on top of the current installation, thereby refreshing the macOS version currently running. That is assuming that the drive device and volumes are healthy.
If you have not backed up your Mac, then this may be a hard lesson if things go sideways.
To non-destructively reinstall macOS as a troubleshooting measure - without deleting user files, documents, pics and vids, etc. – boot your Mac in Recovery mode by restarting and when you hear the startup chime press the Command-R (⌘R) keys until you see the Apple logo and progress bar. Use a wired USB keyboard for this.
Follow the onscreen instructions to “Reinstall macOS…”.
How to reinstall macOS - Apple Support
NOTE– You should not have to delete, erase, format, partition or otherwise alter your startup disk for this. If that becomes an option, quit the process and restart your Mac. Then come back here for additional advice.