Right now, we do not know completely. It all depends on what astronomers determine to be the average density of the universe. There are three 'classical' solutions; one is the closed universe which means its 3-d space is bent around to form the surface of a sphere or some other closed figure. The other two solutions are for infinite universes, either with flat or hyperbolic geometries in 3-d space. At every age, its space is always infinite, and we cannot imagine what the overall shape of an infinite universe is, other than to say that, for small regions, its geometry looks more like a flat sheet of paper or the surface of a saddle on a horse.