Thanks but I would like to know if I win 500 EUR from 200 EUR then does it mean i could withdraw 300 EUR and leave 200 EUR on my wallet?
That is correct. You can see the Terms and Conditions section of the site for an official statement.
I want to nuance this a little bit...
If you deposit 100€, you get 200€ bonus = 300€ total. Win 500€ in total. Than you can withdraw 300€ but you loose your bonus of 200€. This wager free bonus is nice, but it is no free money.