Is Giambit a reliable BTC exchange?

I dont know anything about cryptocurrency or coin or something like that, but last day I received a message in Discord with a promo code, it said activate it and I ll have 0,3 BTC. Wanna ask if there are anybody have used Giambit can tell me the way to transfer it to cash? 🙁 . And I dont know if its some kind of scam, because I dont know anything about cryptocurrency at all.