Leo,
It sounds like you are dealing with a ransomeware infection. It is a type of malware that gets into your computer and immediately starts encrypting your files. Often it stuffs the affected folders with readable .doc, .pdf and .jpg files that tell you that you can pay to get your files back. Don't send money ...the part about getting your files back is bullshit.
The toxic program that is ruining your files has to be identified and removed from your computer ASAP and it may have already cloned itself to be running simultaneously under more than one named version. The encryption program will still be running in the background unless you identify it and shut it down.
You may need an IT guy to identify and purge the malware program because they are good at hiding from virus scans. Turning off the computer should pause the file destruction.
The only defense is having backups of everything. The virus will find every drive attached to your computer. The only safe backup is one that is completely detached from the computer.
XStretchified