Closed Universe

I always fascinated about space science. I got interest in this area when I was in 10th Standard. That time I had a book which is translated from Russian language to Telugu.

We feel like we are living in the three dimension world (here I am not considering time as another dimension). Think that our universe is a four-dimensional sphere or ellipsoid. If this is the case our universe is closed . Anyway we cant imagine 4D space. But if our universe is a 4D sphere then there is radius that means there is limit . If there is limit we generally assume there is start point and end point. Here there is not start or end point. In this case space is curved and formed a 4d-sphere. Assume Sphere and it is very big if you are in surface it looks like a plain area but actually it is curved. Closed universe space is curved in 4D-Space.