This is nothing more than a form of VAC error; you won't receive a ban because of it.
If you received a VAC ban, you wouldn't receive a warning about it.

You will only receive a VAC ban if you have cheats on your PC or if a linked account subsequently receives such a ban.

There are also many possible solutions to solve the problem.
A few examples:
A) Restart your PC.
B) Restart Steam.
C) Run the game as an administrator.
D) Check files for errors.
E) Go to Local Files and click on the 'Verify Integrity of game Files' option.

Originally posted by Lufia:

This is nothing more than a form of VAC error; you won't receive a ban because of it.
If you received a VAC ban, you wouldn't receive a warning about it.

You will only receive a VAC ban if you have cheats on your PC or if a linked account subsequently receives such a ban.

There are also many possible solutions to solve the problem.
A few examples:
A) Restart your PC.
B) Restart Steam.
C) Run the game as an administrator.
D) Check files for errors.
E) Go to Local Files and click on the 'Verify Integrity of game Files' option.

Thank you, but are you 100% certain that is the case?

And I did most of things you suggested, the error appears again after a while.

And to clarify, to run dota as administrator I need to go to \Steam\steamapps\common\dota 2 beta\game\bin\win64 and set dota2.exe to "Run this program as an administrator", thats it?

As I said, these are just a few examples I know by heart; you can probably find more possible solutions by searching the internet.

Yes, I'm absolutely sure. I've been active in this part of the forum for a long time, so I can reassure you.
If you were truly the target of a VAC ban, you wouldn't receive any warning at all. The word "VAC ban" would suddenly appear on your profile, and you would also receive a message in-game.
You deliberately don't receive any warning or indication of when you were selected for a VAC ban, so that cheaters have a harder time developing countermeasures.

Originally posted by Lufia:

As I said, these are just a few examples I know by heart; you can probably find more possible solutions by searching the internet.

Yes, I'm absolutely sure. I've been active in this part of the forum for a long time, so I can reassure you.
If you were truly the target of a VAC ban, you wouldn't receive any warning at all. The word "VAC ban" would suddenly appear on your profile, and you would also receive a message in-game.
You deliberately don't receive any warning or indication of when you were selected for a VAC ban, so that cheaters have a harder time developing countermeasures.

The message didnt go away and now I cant start matchmaking.

Do you have more advise for that?

You could also try this; it might help:
https://steamhost.cn/steamcommunity_com/discussions/forum/9/2828702372991195767/

Originally posted by Lufia:

You could also try this; it might help:
https://steamhost.cn/steamcommunity_com/discussions/forum/9/2828702372991195767/

As I said before, I did most of it. Some things just didnt work

Okay, I thought you hadn't tried everything because you simply didn't try.

Unfortunately, I've already written you all the options I know of.

As I said, all you can do now is search the internet yourself to see if you can find further solutions.