ok, theres a lot of misunderstanding here.
from a right handed pitcher:
4-seam fastball = straight backspin
2-seam fastball = backspin but with an angle like this /
sinker = the exact same thing as a 2-seam fastball but thrown down in the zone so instead of getting more of a left to right action you get downward action. a lot of it is due to the fact that you are staying on top of the ball a little bit longer because you are throwing it lower.
screwball = a ball with top spin with an angle like this \ that goes left to right and down but acts like a breaking ball instead of a fastball with movement.