Why do you think that God exists? 🙂 Because someone told you? Because someone had to “create this world”? ….Why?
If someone told you, then you need to ask that person. If you think that someone had to create this world; then according to this knowledge which we call Gyan; you will learn in a reasonable way that it is impossible for God to create things.
Now, if you put your time into understanding this knowledge (gyan) then you will find out who God is, just like any other religion may tell you about their own version of God. At that point, you may choose to “believe.” We are full of “believers” in this world.
Nevertheless, if you experience through meditation or some other means who you truly are, then you will know God. Not because you are God, no… but because in that experience there is no separation between “you” and God.
You are a “soul.” God is a “soul.”
Unless you become like HIM, you will not know HIM…. but yes, there is always good information about God, however, information is not knowing, it is “reciting,” it is talking, convincing, etc.
If you become like Him, certainly… you will know.