How can you show by experience that the gas produces pressure on the walls of the vessel in which they are located?

The simplest experiment that will prove that the gas acts equally on all the walls of the vessels in which it is found is a balloon. So if we inflate a balloon and assume that it is absolutely airtight, we will see that the air (our test gas) has occupied some volume. Now we squeeze the ball in some place, as we see, during compression, another part of the ball is inflated, which indicates that the gas opposes the walls of the ball with the force that was applied to it, which means that the gas equally acts on all the walls of the vessel.