erase my system data

Why do you wish to delete System data?

It's generally not a good idea unless you intend to wipe and reload the Mac operating system.

If you are trying to make storage space available, start by moving photos, music and videos to an external drive and then deleting them from the internal drive. Those files tend to take up the most storage space.

If your Mac is running slowly and you're trying to find a way to speed it up, deleting system files is not the way to do it.

We could use some details from you before we can give you the best answers.

Please see: Writing an effective Apple Support Communities question - Apple Community