h=-9.8t^2-s, solving for t?

(I don't know the exact wording of the problem, and I apologize for any vague details.)

A ball is dropped from 11.6 meters. How long does it take in seconds for the ball to fall? It is represented in the equation h=-9.8t^2 - s, where h is the height of ball when it stops falling, t is the time it takes for the ball to fall, and s is the height the ball is dropped.

So s=11.6, correct? It would be h=-9.8t^2-11.6. Wouldn't h=0, as well? How do I solve for t, the time (in seconds) it takes to fall?

There is also a second half to the problem; if the height the ball was dropped was cut in half, would the time it takes to fall be half as well?

If possible, I need help to this literally ASAP. Thank you VERY VERY much!! (: