A bad sz joke

I’m not good at jokes but just made this up:

Some guy on the street says hi to another person.
The person responds I am not hearing you, your not real and are just a product of my own mind. The random man then replies to him, Not you, I was saying hi to the person behind you. The guy responds, “Oh,” and life just continued on as usual.


Good joke. I like it.

I don’t get it. But, I don’t get most “jokes”.