Belief in a deity does not prove its existence. Whether an individual is a Christian, Jew, Muslim, Hindu, Bahai, Shinto, or Jain (I exclude Budhism as it is more a philosophy that people bring their own religion into), their religion remains...a belief...not a fact. You can "believe" your particular religion is a fact, but it remains only a belief.
Humans once believed that the Earth was the center of the universe, we of course, now know through science that we are but one small blue and green planet circling on the fringes of an enormous galaxy, which harbors billions of stars and even more billions (or trillions) of exoplanets, of which, some must have other life forms. Humans once believed that a deity pulled the sun around the earth. Science obviously did away with such superstitions.
The Big Bang was recently proven and it occured billions of years ago. Prior to that, the universe still existed; the Big Bang just created that which we can visually discern within our technological capabilities.
Science remains the answer to that which we do not know and through its methods, is leaving less and less room for such things as deities.