but their simply making an act to regain its power by creating an online ways of fiat payments for any transactions.
I guess you mean CBDC's right, well mind you that they are not decentralized, so there's no need to worry about them, they are only digital fiat currencies and aren't going to be used like dex cryptocurrencies.
what would happen if the world abolish the use of paper-made money and adopt whole-heartedly the effectiveness of cryptocurrencies?
The world can't do that, no matter how many countries launch cbdc's, nor despite the rise of Bitcoin or other dex cryptocurrencies, fiat/paper money will be used in every country.
fiat or crypto? or both?
gold or crypto? or both?
Fiat, cryptocurrencies and gold, all or them is going to be used, though Fiat will always be used more than the rest.