It's better to say that you bought them at an expensive rate!
Since when the taxation will be calculated, it is taken from the profit.
If you bought bitcoin expensive, but its price has fallen, then you do not have an income, you have a loss, of course there is not much to pay!
But then they`ll ask for a proof of that purchase. Can I just say I bought it from an individual and there is no proof?
Also why should I not just say it`s a gift from a family member?