Can someone explain for me how the exchanges is making money when I use their leverage service ?
Do they make money also when prices goes up and I earn money ? Or only when prices fall and I loose my money ?
Exchanges earn on fees that you pay when you make a trade. When you have more money at your disposal (even if it is not your money), you would go for more trades, and the more trades you make (whether profitable or not, though honest exchanges are interested that you would stay afloat as long as possible), the more money the exchange earns from your trades. Pure arithmetics.