From Mechanics

As the ball becomes more and more compressed the force that the surface exerts on the ball increases and its speed decreases. The maximum force is when the ball has zero speed and starts to move upwards. As the ball becomes less compressed the force that the surface exerts on it decreases.

The force on the surface is equal and opposite to the force from the on the ball.

The following figure shows the train of events. Time is from left to right.