As for the volatility of bitcoin coins - very high. But take a graph of the growth of Bitcoin for the entire period, at the beginning of the journey there was a constant growth, then it constantly fell. There are waves in nature - there will be a big climb, but when it is difficult to say. Maybe soon, this year, or in 2019, let's see. Investing in digital coins is a noble and risky business.
The strong fluctuation of Bitcoin and the altcoin is characteristic of the cryptocurrency market due to many factors influencing and trading volume is low. I think that when the cryptocurrency market is strong enough then Bitcoin will be better because it will no longer be dominated by big investors.