This is my first time to hear the Suncoin platform and it is totally fishy to me. If you going to buy any digital currency or cryptocurrencies it's better to use a trading platform or exchange site. There are many untrusted exchanges and some of them are not legit that's why you should choose a good and reputable exchange or trading platform just like Binance exchange and Bittrex. If I were you do not use the platform that your friend recommended.