Buy Bitcoin can be considered as a long-term investment for more than 5 years, in turn, there is no guarantee that they will not depreciate or will not disappear from the market at all
As market has sink in last few months at present buying is the better option if not for more than 3 years you will definitely make a better amount of returns from this market than compared to any other market if you invest in it. Though you should have investment everywhere but should not miss crypto curency too.