Existence means having a physical persistence in a segment of time. Science has shown us that time may have begun with the Big Bang. If so, hat would rule out the existence of anything before the first moment. In fact, the phrase "before time" makes no more sense than referring to a land south of the south pole.<quoted text>
God always existed !
Or, perhaps, time always existed, and our universe as well.
It is special pleading to insist that something could have always existed, but that that something must be a god. There is no reason to believe that that is the case. The god hypothesis adds nothing.
You don't answer the question of where everything came from with a god, because you are left not knowing where the god came from. And if you don't care, or don't need an answer, don't bother us insisting that you do for our world, especially when you reject all scientific speculations like eternally oscillating bang-crunch universes, multiverses, and uncaused singularities. They work as well as a god with much less complexity.