1) what lead you to the conclusion that god does not exist?

2) if god does not exist then how the existence is possible?

I mean that nothingness can not produce existence

Well we believe in what we can see and study. Faith is useless. And what is your evidence for the existence of God? if its 'we exist' well that proves nothing other than we exist. If there is a god he doesn't care about us. If you think that the God of the bible is real well… that book is so full of holes and contradictions its almost comical. And this is coming from a person who was a christian zealot for a few years. I started seeing the holes myself, always insulted and fought against atheists NEVER listening to their rationality and listening to christian pseudo-science. When I learned of scientific reasoning and structure I realized there almost certainly is no god, religion is detrimental to human advancement, and its not even a really big deal… no worries or wonders about hell or any wrong faiths. When we die, it`ll probably just be like before we were born. No conscience existence, hence no fear or sadness.

As for reasoning the existence of God. If your really curious, even if it scares you more uber-religious types… all I can say is watch atheist videos, and scientific videos. Compare them with the hilarious pseudo-science of creationists. It took me a while to finally become an atheist but I feel like I've come out of being brainwashed.