the stablecoins centralized are reliable ? Is there a risk that they will be stopped or closed by the usa or european government?
How come they could? Even USDT claimed that they're backed by USD, government has nothing to do with it.
if i have stablecoins centralized is better to convert everything in decentralized stablecoins ?
You mean like USDT? Stable coins is somehow good and life saver especially when you're taking profit or some of your altcoins could possibly dump. However, better to dig up a research hence our advices here our subjective.