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I completed the survey and its displayed for me in the dashboard. So yes, it is free.

I have also 500$ but what can i do whit that?

For now nothing. In the future whenever you would have to pay a fee for transfering fiat or crypto it will be deducted from the 500$ you just received. If you are not going to trade on this site or invest fiat its probably not going to be worth much to you.