i see a short video in youtube and i try to seek more information about, (coinmarketcap, coingecko, etc)
then i post a question here if another user has know this exchange.
There are scam videos on YouTube, there are many of them that I have seen before. If you see this one on YouTube, it is just a scam video. And they will likely comes with big offers to attract you so that you can pay to an address on the exchange which is a tactic scammers use to scam people. If you want to know if an exchange is legit or not, first start by checking it on Coingecko or Coinmarketcap. If seen there, then you further your research, like ask about it on this forum if the trust score is low. But asking on this forum as it is not see on those sites is also very good, you are welcome and you can always ask such a question.