Does someone has any suggestions how to make 17 BTC with 7 BTC starting capital in short period of time?
There is no sure way to earn that amount of money in a very short period without risks the only way that i could think of that can double your money by nearly 100% are gambling which is very very risky , and trading which is the best option especilay if you use the 1 min trading in some sites , i earned a lot from those.
The only way to make 17 out of 7 in a short time is to engage in some illegal activity like black market trading or smuggling. Think about it, we're not even talking about doubling the investment. Sites that say you'll get ROI in a month are shown as examples of pyramid schemes and he's asking for a way to get over 2 times more. It's good to dream though.