Would it help if you knew that time can be curved too? It can. Spacetime is 4d, but if you had one spatial dimension than the spacetime is 2d and each point in the 2d object corresponds to a time and a place.
Imagine rolling a piece of paper into a cylinder. If time is the part that goes around a circle you could have a circular time but attaching the edges together, or you could have a big bang and a big crunch at the edges of the paper. But the unrolled end could be infinite in length. Always was and always will be be.
Or if you imagine rolling the piece of paper like a number six you could have the past be finite and the future go on forever. And the other unrolled direction can be flat and infinite in length, and again it always was and always will be.
And since spacetime isn't actually a surface in a larger space the kinds of curvature allowed are even greater than what you can imagine by rolling pieces of paper. Because its a more generalized kind of curvature.