Bitfinex changed policy. I earned less than I expected. I did send 0,35 BTC and margin short 0,7 BTC at there. I earned 0,70 BCC for 0,70 BTC on my wallet. But Bitfinex gave nothing for 0,35 BTC in my margin wallet. (which they promised to give)
To sum up I did buy and sell 0,7BTC and earned 0,35BCC for free. :) I would have earned 0,5BCC or more if bitfinex wouldnt change anything. And also if i had enough capital it would be a great opportunity. So much effort for only 0,35BCC but it was an unrisky move.
Thanks. It was a great learning experience.