Files in documents and downlaods mysteriously disappear

I'm baffled. Most of the files and folders in my documents & my downloads are gone. I'd say about 95%.

I cannot find any patterns in which files have disappeared.
In my documents it seems to be completely random as far as I can tell.
In downloads all downlodas older than a week are gone except two PDF files from October 2014.

My picture files, even ones edited recently, do not seem to be affected.

I've installed steam a couple of days ago but I can't see how that could have caused anything like this.

I appreciate any help in tyring to recover my files. The most recent backup I have is 30 days old

I'm trying a Malewarebytes scan right now.