Catapult

Can someone please help me wit the programing of a catapult i built

it is tanks style drive
3 motors driving tank on each side
2 motors driving the catapult
2 limit sensors to tell me when the arm is up and down

the problem i am having is that the arm comes down way to hard and because i manually have to reload the tennis ball every time, i want it th have a switch on the robot so once the arm has been fired, it will stay out until the button has been pressed, so i can let it down softly
can someone please help me put this into code?

could you perhaps show a picture of this robot, im having a hard time of understanding how exactly it works.

yea agreed with above, then i would be happy to help