crypto is volatile so here is no safe way to invest in bitcoin.everyone knows that investing in bitcoin is worthy but if you meant about investing bitcoin in online paying sites i will say you will lose all your bitcoin.
Of course, It's not safe to invest in cryptocurrency because they are so volatile, but the most of us know that this community will grow up more in the future and automatically crypto value will increase too, so mostly we will make a profit, as you said, Investing bitcoin in mining sites or any other site it will be so risky, but if you buy it and let it in your wallet it will be a good investment, someday in the future you'll not regret about that.