As you see, the ball is going slow at it crashes into the bricks, but then it speeds up again! How can I make the ball lose kinetic energy as it crashes into the bricks instead of having a constant kinetic energy?
Deselect the button with three dots on the always sensor. You will have to turn up the force value to counteract this though. What is happening at the moment is that the always sensors keeps on triggering and add more and more force to the object. You should just have an initial force instead. Depressing the button makes it only fire once.