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.
Wait for the value of bitcoin to decrease. There are many factors that trigger bitcoin's volatility like the rate of adoption for bitcoin is is being interfered by the news or the media. This kind of news scares potential bitcoin users and they are being forced to not invest in bitcoin at all. Watching or hearing bad news about bitcoin, triggers hesitation to potential users so mass adoption is progressing very slowly.