The proof of God existence is this universe. God created the universe.
Firstly, just because we may not know exactly how the universe came into being it does not automatically mean the answer is "God did it".
Why the universe is not the proof? Toyota for instance is the proof that japan does exist.
Not quite the right comparison. Even if you wanted to assert that the universe was created by something it doesn't mean that just because it exists that it would have had to have been
your god that did it. If you buy a toy that is marked as "handpainted" and it has a toy manufacturer label upon it you may know that the toy came from that manufacturer, but you do not know the exact person at what plant actually had that toy in their hands and painted it. Made that toy specifically. The universe, even if you believe was created, does not have a label upon it. It wasn't signed. You may
believe it came from a deity, fine, just like the toy came from a manufacturer (which could be assumed even without a label), but what makes you think it is
your deity?
Fact is, no, we do not know exactly, without a doubt, all the mechanics and causes of the universe itself, and we may never know, and...that's okay. In the grand scheme of things it's not something we really need to know, it's just something we're curious about. However, just because we don't know something doesn't mean that we must fill in what we don't know with "god". That's known as "God of the gaps". And even IF one really felt they had to stick a god into that, and other, gaps, why certain particular gods? There is no signature upon the stars. Nothing saying that it had to be one particular idea of deity and it couldn't be any other.
So, simply, the universe is NOT an argument for your god, or any other. If you want to claim you can prove the existence and supremacy of your particular god then you have to do better than that.