Malware evading antivirus scans

My computer is running very slow at times, mouse sometimes moves on its own, and while browsing the net it often just closes all screens. Windows defender shows system is clean. I noticed a file on my computer and ran it through virus total and intezer. It shows it’s clean but looking through the strings 3 files show up Java ATM malware, PyXie, and Quasar Rat. Plus a ton of stuff teamviewer. My question is if the scanners say it clean but malware is found in the strings is it actually there? I apologize for my lack of knowledge in this area, and it probably sounds like a Stupid question.