We knows that the crypto currency investment can give us lot of profits even in short time but this is very new there are lot of invesments like real estate,gold,mutual funds silent partner in businesses and lot more but what you think which has highest ROI in short term other than crypto invesments.

My opinion is that real estate can be that one,since my grandfather used to be like buying and selling the lands and made tons of money in his life time but I didn't do that such kind of traditional invetment.