If you could solve one mystery about the universe, what would it be?

I would love to know who actually let the dogs out

Blackholes. Where do they lead? What happens to all matter beyond the event horizon? Is there a multiverse?

And, is extra terrestrial life existent in different galaxies? Can the Fermi Paradox be defied?

What is the secret behind the Bootes Void? Why are there so few galaxies?

Is the concept of time true? Or is it a social construct of humanity that limits us from reaching new horizons?

 What came first, the chicken or the egg??

I would like to solve the mystery of Big Bang ; I'm no way related to Science to authoritatively discuss this topic; So, I humbly present a concept from my imagination : Before Big Bang, universe was a compressed spec. What if that spec might be a compressed vacuum of space - time - energy and mass ; a compressed time frame inside the cosmic microwave background? Just imagine a small elliptical bubble inside a big elliptical one. And the small bubble is expanding in an elliptical path. It is being said that the universe is still expanding. If the space-time is moving like a fountain, from the center of Universe(the point where the Big Bang happened) , everything will go in a downward motion while reaching the crest. And is this why , it feels like everything is moving beyond the cosmological horizon? I've scribbled my concept below..

 A complete understanding of the human brain and how to convert consciousness into a computer program.

the mystery I would like to solve "are we the only high intellectuals beings in this universe ? if no , then where are they , why can't we communicate, although with all the advanced technology we invented , still can't we reach them , why are they still hiding !? "

How babies born knowing how to suck?