Do your research, you might come off as less foolish.
Also...the God belief is that God always existed and was able to magically create something from nothing.
What I tend to argue is that perhaps matter has always existed (as far as I am aware, this only exists as a hypothesis). Thus there's no "something came from nothing" argument, at the current point we don't know where matter came from, if it indeed came from anywhere. It's just scientists can look as far back as the big bang. We simply don't know anything about the Universe before that point, therefore, it's actually difficult that the Universe came from nothing, but this is what creationists use as a strawman for some reason.
What's even more foolish is that you've labelled it atheism...it's not, it's the Big Bang Theory, a scientific theory in NO way connected with atheism. Atheism is the disbelief in any deities. The Big Bang Theory is accepted by some Christians and other kind of theists, arguments such as the cosmological argument can exist alongside the Big Bang Theory, because to them, God is the 'unmoved mover and uncaused causer', thus the big bang would be the first 'cause' or first 'move'.
Pick up a book, talk to atheists about what they believe, read up on the science before you think you can make any contradicting points. Without that, you're relying on strawmen arguments made by creationists. Creationists very rarely have a clue about scientific arguments, because they can't be bothered to learn about it properly. Never listen to a creationist who starts talking about how science works, because you'll quite likely find that they're talking a load of rubbish.