I believe this last question is the key one. Rather than wondering about the right time to buy and sell, the OP should establish the time horizon for the investment. It seems that he wants to play at buying and selling in the short term, which means he is likely to lose his money. Even worse would be if you are considering buying to make money only on the rise but are worried about a fall because that is the typical behaviour of retail investors who buy high and sell at a loss out of fear.

Ideally, investing money in bitcoin that you will not need for at least four years (one cycle) is likely to work out well.