Let's imagine for a moment you come across an open door. What opened the door? There's an assumption in that question. You assume there was a time when the door was closed. Now, in order to attach a door, you need it open. If it's closed, you can't reach the hinges. So, it is entirely possible for a door to spend its entire existence open.
Through this analogy, you see the flaw in asking "if God created everything, where did God come from?" Just as it's possible that there was never a time when the door was closed, there was never a time when God did not exist. Therefore, God does not need an origins story.
The heavens, the earth, and everything within them, however, do. There was a time when humanity didn't exist. There was a time life didn't exist. There was a time the earth, the celestial bodies, the distant galaxies, did not exist. In fact, due to the impossibility of traversing an infinite amount of time, there must have been a finite amount of yesterdays in order for there to be today. In other words, time itself did not always exist, and needed a beginning. As the saying goes, there's a first time for everything.
There are a lot of possibilities for the origins of the universe, but by far the best explanation is the God of the Bible. He's the only Creator with all the necessary attributes, and He's the only God who actually stepped into human history. And not just by appearing as pillars of fire or smoke. He stepped in as the man, Jesus Christ, who lived a perfect life, died a sinner's death, and most impressively, He rose from the dead. Why? So that if you believe in Him, you can have eternal life. Personally, I'd rather take that than anything men like Lamitre, Lyell or Darwin spat out.