The point is that we cannot know what exists at a distance of 13.7 billion light-years from us because, relative to us, that part of the universe has not yet been created. There is nothing there. And for this reason, it is impossible to determine the actual size of the universe. Although there are assumptions that its duration is no less than 90 billion light-years. But neither the human mind nor human instruments will be able to provide all the answers with certainty for a long time.

By the way, the shape of the universe has not yet been discovered by cosmology. There is a big question mark here.

Incidentally, there is such a theory in philosophy... I won't say the name because I might be wrong. But the essence is that there is no elementary, indivisible particle, just as there is no maximum large cluster of bodies. That is, the universe is not the limit; there is an incredible number of such substances (if I may express it that way) that, instead, create something even larger. And so on – infinitely... :)