Eg.
If you can break through the Universe, what is there?

and also, some people beleive in the big bang theory. well, if the big bang theory was true, how could there be a bang without any matter to begin with?

eg.

The universe is defined as somethingness and anything outside of the universe is defined as nothingness. When something from the universe enters the nothingness, the nothingness becomes somethingness and is now part of the universe.

Question: Why is the Universe here?

Answer: Where else would it be?

By definition, those of us in the Universe (i.e. everybody we know about, and then some) can't know what came before or caused the Big Bang, because that is literally the moment when Time itself began for this universe. I can't even come up with a good analogy for it because every single analogy presupposes that we can "get outside it" and observe it from that perspective.

It is entirely possible that some creating entity is responsible for the Big Bang. But there is absolutely no way for us to know, because we can't step out of our Universe. (You can believe whatever you like; believing doesn't necessarily make it so. Then again, your beliefs might just be correct to ten decimal places. Who knows? Not I.)

It is possible that, if the universe is closed in four-space, if you were to attempt to fly out beyond the edge of the Universe, you would eventually return to your starting point. If that's the case, then the "expanding universe" could be the four-dimensional surface of a five-dimensional sphere whose radius is continually increasing.

Your question reminds me of a BC comic from a few decades back.
Remember when Peter proclaimed himself "The Smartest Man in the World"?
Well, one day he explained to his companions where dew comes from:
During the day the sun's out and it's warm, then at night it's cold. Consequently, when we wake up in the morning, there's dew all over everything!
"You're a genius, Peter," B.C. said.

any more for list?