Finaly i want to know if that person can get into our computers only from the game.
Impossible.
Just found out he accessed my files as all of my ship design files are missing now
If thats the case you'll have to worry about a lot more than just SSE-MP.
People cannot hack into other computers just by playing ShipSim's multiplayer. If you are certain someone else removed your content, then he has access to your computer, which includes, but is not limited to ShipSim Extremes.
In such case, there is nothing VSTEP can do about it as this problem isn't SSE related. I would advice you to take your computer to a computer Expert or someone who knows how to track the executable that the hacker is using to gain access to your PC.
Regarding the MP abuser, I will report this issue and ask if VSTEP can provide me the MP logs.
On which server did this happen?
And to make sure, which user names did he use?
He got so bad I just IP banned him from joining my server with a IP blocker I got.
Can you send me this IP address through PM? It can help tracking him down.