A metaphor I’ve always liked is the raisin bread one. In this metaphor, the raisins are galaxies, and the dough/bread is space-time. When you bake the loaf, the dough rises and expands. And once the loaf has finished baking the raisins are now farther apart than when they started. But they aren’t farther apart because they moved through the dough away from each other. They are farther apart because the dough expanded. The substrate they exist in expanded, space between them expanded, and now they are farther apart.

So when we talk about the universe expanding, we aren’t talking about galaxies simply drifting farther away from each other. We are literally talking about space itself expanding. The emptiness itself between galaxies gets bigger. And that process can happen faster than the speed of light.

It’s also worth noting (and I’m not that up to date on this so someone correct me) that the Big Bang isn’t like everything just started expanding from a single point at the speed of light. It’s more like all of a sudden everything just was. Not instantaneously, but in a matter of seconds the early universe just was, and it was big (millions? Billions? of light years big). And from that point it began to rapidly span outwards. And again, the Big Bang wasn’t all of a sudden matter exploded into the empty space-time of our universe. The Big Bang created our universe. It created space. Before it there was nothing. Not nothing like empty intergalactic space nothing. I mean like no-such-thing-as-empty-space nothing.

So yah the universe can expand that much in a short amount of time.