the one issue with physics that i have never really been happy with.
The big bang, there was nothing, no time, no mass, no void, absolutely nothing, then there was everything, time began, mass and energy appear.
As for the shape of the universe, you have to remember that space is not 3d in the normal sense, time, gravity, mass, energy, everything, interact in ways that on an everyday level you do not see. You assume time is fixed, but it is not.
dont question the scientists, unlike the religious people their right about every thing!!