Has someone accessed my mac folders? SECURITY

It's been a few years since I bought my MacBook (MacBook Air (Retina, 13-inch, 2018). Back in February 2019 I started noticing some strange folders on my computer which I could not access. Once I began to try to access them, my computer completely shut down TWICE. I gave up and in 2020 tried again, same thing happened, so I completed mac recovery and managed to reboot my mac to a "clean slate". However, there are still some files and folders which say "private" and "hidden" and which I can't seem to access and I most definitely don't recognize. Could someone tell me if these are build in system folders or if something else could be going on? What are they? My job requires some research which could anger some people out there so please try to go easy on me for the paranoia.

In short, I just want to know if this is normal or not.

Thank you for your help. I AM DESPERATE.