Who is winning and who is loosing in forex

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Today i had an argue with one friend of mine about Forex trading. He said that if you win in forex, you win the money of others traders who lose. I think that if you lose money in forex with margin trading you lose your money, if you win the one who lose is the broker who give you the money for the margin transaction. Does anyboy knows the true, about margin trading in forex and who win and lose?