Safari keeps opening random tabs with URLs that change

This only started happening recently, I must have downloaded something dodgy. Does this mean my system is compromised? Im not a computer guy so I'm not fully sure what a compromised system means. I read a thread similar to this that mentions a compromised system. Ive just downloaded Malwarebytes to scan for viruses, will this do for helping remove viruses?

If you could explain whats happening to my computer, how I can save it and how to backup necessary data (if needs be), that would be awesome!

EDIT: Just ran a Malwarebytes scan and it found 6 threats and told me to ‘restart for quarantine'. I restarted my Mac as instructed, ran a new scan now it says I'm clean. In the ‘Quarantine' section, theres now some weird background/secret computer files (sorry, not sure how to explain it. Screenshot attached) which I'm assuming are corrupted/infected in some way. Should I hit ‘clear quarantine' and then thats that, I'm fine? Sorry for so many questions haha, I'm uneducated.