>It'a quite clear after you understand semi-advanced physics that nothing could exist before the universe started.

The implicit argument here is limited to the type of things that make up the universe we can see and observe. It would be most accurate to say that the things that make up the universe could not have existed before the universe started. Philosophically speaking we can't preclude the existence of things that could be of a different type, or exist outside our own universe. It's the same problem explored in Plato's cave.