Nobody knows what ultimate reality is, which religious believers call "God." All we have are guesses, some more defensible than others.
Here's mine -- after some forty years of delving into mysticism, spirituality, religiosity, and philosophy.
Subject to change, of course. If I've learned anything, it's that there's always more to learn. Or guess about.
I'll be as pithy as possible, a shift from my usual wordiness.
(1) God doesn't exist. Not in the sense of an all-knowing, all-powerful personal or individual consciousness. Or even a universal consciousness, though this is more likely than an anthropomorphic God.
(2) The cosmos is, always has been, always will be. In some form or another. Existence always has existed. If you want an eternal "God" to worship, there it is: existence.
(3) It may well be that our universe is just a very small part of the cosmos. But reality is thoroughly natural, not supernatural. Other universes, if they exist, are as natural as ours.
(4) We'll never understand the ultimate laws of nature. Or even know whether they exist. "Ultimate laws" probably is a human conception, not the way things really are.
(5) The biggest problem with being a member of Homo sapiens also is our biggest evolutionary advance: self-awareness. We are aware of being aware. Unlike other animals, we construct an ego, I-ness, by looping our awareness back onto ourselves.
(6) This creates a fear of death, because we know we're going to die. This creates a desire to exist forever, because we can ponder our non-existence.
(7) Thus springs up religion. Along with notions of God, soul, spirit, eternal life, heaven, and such. All are products of a self-created "self," which actually doesn't exist in the sense a stone, sunflower, star, or snake does. It is conceptual, not physical.
(8) Enlightenment -- seeing reality as clearly as possible -- is recognizing that ego, I-ness, selfhood, individuality, or whatever you want to call it doesn't exist.
(9) We're part of the cosmos. And the cosmos is part of us. We just happen to be beings who can conceptualize ourselves as separate from everything else, which we really aren't.
(10) So when we die, we're dead, inasmuch as "I" consider myself to be a "Me." But the cosmos continues. And so will I. Just not as me. Whether this is a chilling or reassuring realization depends on how much "Me" is attached to my "I."