If I have 0$ at the moment can I make 100$ in 2 or 3 months? How?
What if I deposited 20$ .. Can I make them 100$ in less time?
If your starting from $0 then you'll have to do some work to get the initial money. You can work in signature/bounty campaigns or you can charge for any skills you have such as marketing, programming, etc. If your starting with $20 and you want to trade, you can definitely make $100 in 2-3 months but you can just as easily lose that $20 in the same time period or less.