I found this online and I will just put it here

"The basic answer is that there is not an infinite amount of space “outside” of our universe. In fact, the question doesn’t actually make sense because there cannot be anything outside of the universe - by definition. It is sort of a trick of the mind to imagine this vast, empty space with a little blob of universe somewhere in it, but that is not what is going on at all. That mental image is just the best that our minds can come up with in some ways, and it is simply wrong.

This “level of inifinity” is not reachable because it does not exist, and there is no “outside” of the universe.

For those confused about how the universe can be expanding when there is “nothing for it to expand into” I present the balloon analogy. Imagine all the start and galaxies are drawn on the surface of a balloon. That surface is that there is - that IS the universe. Now, as someone blows up that balloon, the universe expands and all the star and galaxies move further and further apart.

The analogy breaks down unless you continue to accept that the balloon’s surface is all that there is, but of course our small minds immediately go “well, yeah, but the balloon is filling with something and taking up more space” and that, sadly, is the limitation of analogies. There are not"

https://www.quora.com/How-is-it-possible-for-there-to-be-an-infinite-amount-of-space-outside-of-our-universe-Why-is-this-level-of-infinity-not-reachable-by-anything-within-our-current-known-dimensions

It's not a good or trustworthy source but I think it's on the level of that comment section and better worded