so looking at it very well you notice that bitcoin price may rise above 70k or fall below 50k, say I said that is because the price is unpredictable
It is not completely unpredictable. It has mostly been going up since 2010 (when it first got a price), and yeah there have been periods of down, but you will must consider that the trajectory has mostly been up, which justifies considering getting some in case it catches on, and then once you get some just continue to buy it... . there is no reason to believe that it has stopped in its overall trajectory to go up, even if there are likely going to continue to be various corrections (and volatility) along the way.
Perfectly said @JayJuanGee because looking at the way Bitcoin price is moving I think is really good for one to Accumulate more Bitcoin in our portfolio because just as you have said earlier if we check since that time till today will would notice that you are right, because even as at yesterday Bitcoin price $56 but just this night the price have increase to $63 and if we check it now any one who buy Bitcoin as at yesterday that the price was DIP you we see that you have make small profit today that price is up, and I still have strong feeling that Bitcoin will go more higher in the future.