Have you already made any deals or are you just figuring out how to do it correctly? Since you are a beginner, you only need to use isolated margin, so you allocate a certain part of your money to one of the positions, that is, you risk only it. I learned about this from an article on iTrusty.io about isolated vs cross margin explained, you can check it out. As for cross margin, you risk all your money and in this case, even if one position goes down, the system can use profits from other positions that are open. But if all your positions are unprofitable, then you may have to liquidate your entire account, so as a beginner, you should only use isolated margin.