Will there be any sort of fees as a user when trading/exchanging merchant tokens or GAT coins?
When no fees involved, how does Gatcoin generate profit?
I think they must have some fees.. Also part of this fees (for example 50%) must be burt - it will do more liquidity and expansive tokens.

They will generate profits in fees when using their own exchange, as well as the issuance of tokens from shops an retailers, I imagine that the service to create the token of your won shop will have a cost, with a monthly fee too, so if the shop doesn't want to issue tokens, they stop and gatcoin simply burn it.