Infinite...having no beginning nor end.
How big is the entire Universe?
There is no way to tell how big it is. It may be growing every second or we may just be in an alien's fishbowl.
The observable "Universe we know" is about 91 billion light years in diameter. The actual size beyond the observable is unknown.
First thing you have to learn is it is not a universe, it is a multiverse.
Yes it's a fact.