how will people adapt change from FIAT CURRENCY to DIGITAL CURRENCY like BITCOIN?

It is totally difficult and its a long process. Fiat money are totally in the heart of indivuals, I don't think that replacing it with digital currency would happen because probably many people will opposed with this. Actually, we can used both of them and it depend on us which one we are preferred of. So there is nothing to push by replacing it because both of them have doing great and have value in the market.