Will Joyso burn JOY in the future like Binance
What do you mean by burning them !?

I guess he is talking about a feature where a percentage of transaction fee (generated in the exchange) is burned. So let's say the exchange gets 100 JOY token worth transaction fee and decide to burn a part of it (let's say 5%), then it will reduce the totak available tokens continuously and thus increase its demand.
Oh! I read it on the webpage's FAQ that the "unsold tokens" will be retrieved by the team and they will be released in a rate of 15% per year.
So this part won't be burned. Am I right?
Yes. Even I read this. I think they mean to say that all tokens have been generated but unsold ones will be release yearly. Not more that 15% per year. Plus, imo burning would refute the idea of HEX because token has a utility in the system and once they reach their target trade volume and considering the numbers ICOs which can potentially get listed, a good circulation will be helpful.