How to find malware on a Personal PC ?

My pc is having some issues lately. Files going missing or sometimes it feels like somebody has been accessing the pc. So I scanned the whole pc multiple times by antiviruses but I didn’t find anything. Recently my company pcs had similar issues. A cybersecurity firm found a hidden malware that helped let hackers remotely access pcs. I suspect a similar thing on my pc.
I really can’t check my pc with the help of a company. So is there any real way to check if my pc is affected by a malware.

Attach your basic diagnostic logs. (MBAM and FRST)
Instructions: https://forum.avast.com/index.php?topic=194892