The is only one thing that I would do to grow my Bitcoins, and that is to invest them in a reliable company or shares. The way I would reach ROI (it could take longer than expected) 
But nowadays it is so hard to find some reliable company. Ponzi's are everywhere. So much better to do other method than waiting for that "reliable company"*.
It's impossible. I don't trust any of them out there. This is my take on investing at the moment for ROI in the Bitcoin space. Scammers, ponzi schemes, you name it, they are all there. You are the best to leave you bitcoins in the cold storage and just wait to see what the future will bring.
I know this is almost impossible for people to do, since we all want more and more coins in our wallet, but this is exactly the greed that these scammers are taking advantage off!