How do I know when Il get liquidated say I put 30$ in CFDs if the result hits minus 30 then il get liquidated or how can I know when it will close thanks
It depends on the amounts of total funds and blocked funds in your account as to when a position will be closed. You can start reading here in the help pages. Use of the practice account will also help you understand.
This link has a worked example.
If you have just $30 in the account, invest it all in one position and so have $30 blocked funds, then the position will be sold when it has lost $15.