Bitcoin is and always will be very volatile, but this does not mean having to give up his purchase. If you look at the chart of growth rates you will see that every year the price of bitcoin is increasing. This trend will persist for a very long time so you can buy it at any time.
so i should buy bitcoin at this point or when the value reduce.
You should look into buying it when theres something that effects the market, like the Chinese new year that was going and the prices dropped low on that month and it raised back to 11K as we speak.
It is not good to be confused about bitcoin it is nature of bitcoin that it use to increase and decrease with time so just look at the market if in maker price is down it mean you should buy and it is time to save it but if they demand of bitcoin in market is high and price is increasing too then you should sell for profit, on the other hand I would say that instability and fluctuation is the best thing about bitcoin, bitcoin is volatile and it will make price of bitcoin at the peak of all other currencies.