The top 3 mistakes people make about the Big Bang Theory:

The Big Bang Theory does not say anything about how the universe began. It's only a theory about the early history of the universe. We have no empirical theories about how the universe began.

The Big Bang Theory does not say that the early universe was small. It's true that the observable universe was microscopically small. But that is only the observable universe - the entire universe can still be infinite from its very start. We have no idea if the universe is infinite or finite, but it's very unlikely that the observable universe is the entire universe, with us at the center.

The Big Bang Theory does not say that the early universe was chaotic. In fact, the early universe had very low entropy and has increased in entropy ever since. Its entropy was low because the matter and energy in the early universe were extremely uniform and evenly distributed. The universe will once again be uniform at heat death, but the difference is that it will be diffuse, not compact.