hy, the problem on investing and cloud mining is high risk i seen many of companies not run till 3 or 4 month when it's time to get R.O.I mostly programs became scam and loose money with time. But the best way to double your bitcoin is try trading on altcoins because i saw many times every altcoin price is increasing no one go below the trend some increase day by day and some increase monthly but fact is they always increasing so purchase the coin and hold and sell that after one week or month when it's price go higher.