The fact that you aren't sure enough how trustworthy those platforms you have mentioned, then disregard them, even just for now, and consider using those big and reputable* trading platforms today e.g Binance.

The purpose is to start doing trades so no need to test waters on those other platforms. You will be there soon. Not promoting Binance but no doubt, it's a good place for newbies - NO KYC*, better selection of coins, volume, etc. and we like to minimize the risks for them dealing on other platforms.