How is it possible that God existed before anything?

God existed before anything because it is impossible for nothing to exist

The mathematical figure zero does not exist in nature or in reality
Humans invented it as the only way to make their sums add up

Because the figure zero is a complete invention, plucked out of nowhere, then nothing that humans create should work
But it all does
That is proof that the human material dimension is an artificial construction
being operated by an outside force

Further proof is that whatever humans desire, to the point of attempting to invent it, is given to them
Your most honest inventors will admit that they have no clue how they invented it, and are surprised, themselves, that they got it to work

Bearing in mind that the greatest human minds could not create an arithmetic system that worked (without zero), it should not be a surprise that humans can’t invent much. It is all given to them