Al Bid-aya

Does God exist, or not? Yes, or no?
If yes, how best to realise him in this life?
Man throughout history from the ancient Greeks, from the ancient Sumerians, had this idea of God, right?
I am not at all sure whether in the Upanishads and... whether they mention God at all
Or is it a later invention?
So what is God?
I am not attacking God, I am not... denying god
But we are investigating whether there is such a thing as God