If you buy Bitcoin with the idea of selling most of it after, say, 5 years - then you don’t really understand what Bitcoin is.
Most people don’t, and I don’t blame them.
But fear no more! For you have come to the right place.
To understand the thesis of bitcoin, one really must understand the money we have today.
There kinda is not alternative, because it solves a problem you did even not existed.
In order to understand Bitcoin, one must first understand money, and to understand money, there is no alternative to the study of the function and history of money. - The Bitcoin Standard (Chapter 1)
You could just jump to the solution, but that’s pointless. Go through this (how money works), then come again.