Creator’s existence is independent of the beliefs of the creations.
The human belief system is dependent on feelings, fear of unknown and observation. There are numerous forces in nature that the human intellect is unable to explain – gravity, for example.
The question of the existence of God, the How’s and Whys about the creation, is still a stretch of the imagination of general human intellect. That may be the reason for 300 billion religious atheists.
The fact that science has yet to offer solid evidence of how the Universe was created is enough proof that it was created by an intervening Force. Call it God, if you will.
God has communicated with His people in several ways. His favorite ways of communicating with the people were by foretelling a future event or describing the biological process of creation way before it was discovered by science.
Your enlightened idea of the existence of heaven and hell on this earth may be true, but it does not prove that there is no Heaven, Hell or the day of Judgement in the life after death.
Now, how do we know if there will be a life after death? It is the same way the fetus knows about life after the womb of a mother. We do not know. However, we learned about life after death from the same communique that told us how human birth takes place in the mother's womb. That what establishes it.