BoredEngineer, thank you very much for your answer. It helped clarify some things. The game itself does not resemble a pinball or billiard in any way. In the original game (Arkanoid - Arcade Longplay [270] Arkanoid - YouTube), the ball keeps its speed or even increases it depending on the place the ball hits the pad. So, if the ball hits near the corner of the pad, the horizontal speed increases, while when hitting close to the middle of the pad makes the horizontal speed slow down. Of course, that part is pretty much artificial and I would have to apply corrections to make it behave like the classic game (or not, I will choose later).
I have used the materials that come with the starter content. Is that a problem?
And about physics, yes, I marked the options both in the ball and the walls. I will change the scene to remove the default object that is created. If possible, could you please clarify why is a good practice to remove the DefaultSceneRoot object?
Thank you again for your time and help.