we shall assume the price the BTC will have in May will be the maximum for this cycle?
Should we sell in May?
Trading purely based on your assumption will definitely lead to big disasters. You cannot predict the timing of cycle of price fluctuations just from past history. If you have any technical analysis to find out where market will turn up then you may proceed. Moreover all technical analysis are providing only the price ranges not the timelines. I mean you cannot make your trading on timing based but only on price ranges because technical analysis provide only signals on price levels.
Trading purely based on indicators will not be helping you neither in the end, because unexpected things do happen. Emotions are definitely the number one reason why everyone loses money, because if you just make an assumption and call it the truth and make moves depending on that, you are going to end up losing a lot of money and unfortunately there are too many people who do that, don't know why they do it but they do it anyway.
I do not like investing into things without researching very very well, it has to be very careful and make you feel comfortable about it, if I do not know every single detail about the thing I am investing into, I am not going to end up going into it at all. Of course it is not going to be easy but I think it is going to be decent profit if I do that. All traders eventually becomes smarter about it though, that is what I think, they learn with their mistakes.