Unfortunately, we can’t get outside the universe to see what it looks like as it expands, but we can imagine it.
If you took a balloon and marked it with dots and then blew up the balloon, the dots would expand along with the balloon’s surface.
As the balloon grew larger, the dots would move away from each other, just as the galaxies do in our universe.
Keep in mind that even though it is widely believed that the universe is still expanding, many astronomers now believe that one day it might all collapse on us.
Nobody knows when, nobody really knows how, and we’re pretty far from figuring out why.