The shape of the universe, and the curvature of space-time, are two different things. I can understand why it must be confusing when the term "flat" is used to describe one idea for the shape of the universe, but this is different from the curvature of space-time. Good on you for starting to educate yourself, and I hope you carry on. I can link you to the weekly astronomy podcast I listen to if you want. But I also would prefer not to respond to more posts on this subject here, as I am busy with discussing evolution and creationism, and that is in fact what this forum's purpose is.