Depends on your definition of "it all."
Not too difficult, that one, as long as you don't ask for a
precise answer for what caused the Big Bang.
You should do a little checking. They've pretty much nailed down the age of the universe withing a few billion years and there are only two or three theories on how the universe evolved after the big bang to become what it is today. And even these theories are very similar to each other.
This is not one of those things that's hard to figure out.
Just remember, when they say the universe is expanding, they don't
only mean that all the matter in the universe is flying away from all the rest of the matter in the universe. They
also mean that the space in between all the matter is expanding, carrying the matter along with it, like raisins in a loaf of raisin bread that is set aside to rise before baking.
Ever make yeast bread? I do it often. I'm a great cook, in fact

(brag brag brag.)
I love fresh bread but I can eat it faster than I can make it.
Harte