I saw in some comments some people dissapointed or saying poloniex is scam, what do you think?
You will find comments like that for basically any centralized exchange (even the most popular ones like Coinbase and Binance ) so that's that.
Having said that, Poloinex is a decent choice if you are in need of CEX, but that of course doesn't mean that you should trust them with large amounts of money, or use it to store your crypto.