This is one of the few possibilities where you can get such a profit in a short period of time, but the risks are very high. In addition, seven bitcoins is a very high amount to invest in gambling. Bitcoin could already be considered, in my opinion, a good investment for the long term, but it takes time and patience to be rewarded.

There are other investments, as you mentioned... if you are referring to forex, this is also an investment with a lot of potential, but it requires a high level of knowledge of the fundamentals and technical aspects, to succeed in this market and to earn a living from it.