Difficult To Proof God's Existence

How do we know God exists? There is a very good answer from this website, "How Do We Know There Is a God - Answers in Genesis".

QUOTE
The skeptic’s condemning cry often comes as, "Prove to me there is a God." Usually the agnostic or atheist expects physical or scientific evidence for the existence of God, but when the Bible believer cannot point to a living being and say, "There is God," the skeptic thinks he has won.

What people often do not realize is that even if God appeared on the earth (which He has, in the person of Jesus Christ), we did not exist in eternity past and do not know the future, so we cannot prove by any human standard that He is eternal. Our understanding is limited, so we cannot prove that God knows all. And our limited perspective renders us incapable of proving God’s standard of morality as absolute and true. Not only that, but by our own fallible standards, our "telescopes are short-sighted," and we cannot determine if He is the only God that exists inside (or outside) the universe. So, even if we could observe and scientifically test God by our own standards of operational science, we would be unable to prove all of His divine, eternal attributes because of our own limited mortality.

So any answer to the question, "How do we know there is a God?" that does not start with God’s own statements regarding Himself is self-refuting, inconsistent, and limited by human frailty because a finite, limited man can never ultimately prove the existence of an eternal, all-powerful, all-knowing God. Only an eternal, all-powerful, all-knowing being could prove the existence of the God described in the Bible.
UNQUOTE

It is difficult for the finite to prove the infinite, for the temporal to prove the eternal, for the creature to prove to creator.

Have you not known? Have you not heard? The LORD is the everlasting God, the Creator of the ends of the earth. He does not faint or grow weary; his understanding is unsearchable. (Isaiah 40:28 ESV)