Doubler or any Investment Sites is 100% scam / ponzi scheme because they are offering big return in short period of time
I have tried using hyip/doubler sites before and it's base on pure luck and some techniques
Sometimes I earn sometimes I'm not. but I tried my best not to lose any money
There's like :
50% chance of losing your Money
25% chance of getting your money back
25% chance of getting a profit.
It's like gambling, but using dice games gambling sites is better because you are the one who will hold and play your money.
I suggest don't try any doubler sites, It's just a waste of money.