To expand on my last comment the sails each have their own set percentage of speed.
Forward sail being 25% the middle 50% and the aft 25%. Now depending on how you position them in the wind will determine how any combination of the three will affect your speed. But leaving all three down will always make you go faster than pulling any of them up regardless of wind position.
In addition. The sails do not affect turn speed. You will always turn at the same speed for each degree of turn. Pulling your sails up will only affect your forward movement thus making your turn tighter. But again regardless of what combination of sails you have down you will not turn “faster” but instead tighter due to slower forward movement speed.
This is not true for real life. Just the game. If you feel inspired and plan to sail in real life please do separate research on that lol.