Im buying now good amount , seems bottom reached , BUT i will keep 50% in cash in case bitcoin goes down further .
This is the best way or rather, strategy to invest, asking when is the best time to buy is actually wrong because there is no best time to buy Bitcoin or any other crypto currency because prices are highly unpredictable, somebody can tell you the best time to buy is when the price is at $19,000, and you buy at $19,000, only to price go down below $18,000 few hours later.
So the best thing to do is to use the DCA strategy, that is buying an equal amount at every dip while waiting for price to rise.