sharing about Software update

In general, updating macOS does not damage or delete your other, personal files.

However, I would recommend creating a backup of your data before you start updating your Mac.

If you do not have an external hard drive, you could also save specific personal data transferring it to an USB drive, for example.

No, updating macOS will not delete your existing personal data.

Update macOS on Mac - Apple Support

But, having a recent backup created by TimeMachine is always a good idea, just in case.

Back up your Mac with Time Machine - Apple Support