Invariably accounts are rarely 'hacked'. They are merely phished from their owners who are clicking on spurious links.

Originally posted by NuggeT:

4 days ago someone hacked my acount...

Do not trade until your account is secured.

Take the following steps to secure your account:

1. Scan for malware. If you don't have a malware scanner use https://www.malwarebytes.com/
2. Check that the email and phone number on the Steam account are still yours.
3. Deauthorize all other devices. https://steamhost.cn/twofactor/manage
4. Change passwords from a clean computer.
5. Generate new backup codes for your Mobile App. https://steamhost.cn/twofactor/manage
6. Revoke the API key (there should be no key). https://steamhost.cn/steamcommunity_com/dev/apikey

Originally posted by NuggeT:

...they buy 200 dollars in my wallet idk how to rembolse it

They did what?

Originally posted by Community Market FAQ:

How can I reverse or cancel a completed Community Market transaction and/or get a refund?

All purchases are final – you will not have any right to a refund or a reversal of any Community Market transaction once it is completed.