Can the ball hit the walls during a rally?

Yes. After the ball bounces once on your side of the court, it may rebound off your own back or side glass walls and you can still play it legally. A ball returned to the opponents' side may also bounce on their ground and then off their walls and remain in play. However, a returned ball must not hit the opponents' fence/mesh or any wall before it bounces on their ground — doing so loses the point.