3 destinations for pushing is necessary or trade routes would be pointless. Warehouses have an extra 3 for pulling.
What exactly do you find confusing about that whole system? Maybe the answer is in the tutorial...
As for profits, the game is considerably easier in the last patch (will be even easier in 3.1). Just focus on the products wanted at 125%.
Drop by our Discord, there are tons of other players that will give you a hand: https://discord.gg/Q3XyYGM