So I was making a deal with a Hycan player after he had finished his part of the Strategy action. I was going to trade commodities while we were doing the secondary action. But my friend said we couldn't trade because the Hycan plaayer had already finished his action. I am understanding that we can still conduct a transaction up until the secondary actions are finished and up until that player flipped his strategy token (in this case the Hycan player) What indicates the end of a players turn and at what point during that players turn can transactions be and not be conducted? Can they be conducted while the secondary action is being conducted?

The active player, in this case the Hacan, is able to initiate deals at any point in time from the nanosecond that their turn starts up until their turn is over. However, as stated in the rules, they may only make one deal with each neighbour per turn. IIrc, there are no automatic turn-ending steps to any type of action.

At least that's how I play. A player turn stretches from whenever the previous players turn is over until the player states that their turn is over. That way, everyone should have enough time to remember everything they've planned on doing. It cuts both ways, though, since if anyone were to forget to do something before stating that their turn is over: they're outta luck and have to wait until their next turn.