Macbook air

What to do before you sell, give away, or trade in your Mac That is what the previous owner should have done before selling it.

If it is safe to do - take if back to them and have that do this or get you money back

Looks like last user did not do the correct steps before selling. You can use the command-R then use disk utilities to erase the drive and format APFS then reinstall the OS and see if you can use your Apple ID to start up and see if all works correctly..