I' ll take bitcoin as an example.
Is it mandatory that the value of all bitcoins is equal to the value of the world economy?
Can this value be archived before all the bitcoins are mined?
When I buy bitcoin someone will take my dollars.
So how can we technically replace all dollars with the bitcoins?
In the end will there always be someone with only dollars in their pockets or am i wrong?
Bitcoin most probably will never replace fiat currency as the standard money around the world, and it doesn't need to. I'm not sure why a lot of people are obsessed with this, on the one hand it's next to impossible, on the other hand, why would you try to replace fiat currency? Bitcoin and fiat can coexist easily.