You say, " ... nobody knows all things, except God himself ... "<quoted text>
Hmmm! I wonder were you got your information! You know ...... people believe anything without checking things out.
AND ...... please don't tell me I am one of those people because nobody knows all things, except God himself. There is much proof of the flood. You are apparently looking at the wrong info. You sound like a New Ager or an atheist. Take off your blindfolder! If you study the Bible as a whole and not just pick pieces out, perhaps you would understand it better....
Since you completely believe EVERYTHING which is in the Bible, be advised that the Bible clearly shows that your "god" does not know everything.
Presumably, your "god" created Man, including Man's ability to "sin." And -- according to your mythology -- Man SINNED. And your "god" got upset because Man "sinned." And your "god" presumably destroyed most of the living things on earth because Man sinned (when a simple "factory recall" would have solved the problem.)
Genesis 6:5 (KJV) And GOD saw that the wickedness of man [was] great in the earth, and [that] every imagination of the thoughts of his heart [was] only evil continually.
Genesis 6:6 And it repented the LORD that he had made man on the earth, and it grieved him at his heart.
Genesis 6:7 And the LORD said, I will destroy man whom I have created from the face of the earth; both man, and beast, and the creeping thing, and the fowls of the air; for it repenteth me that I have made them.
Thus: If your "god" knows everything, why was he surprised that his creation Man in fact "sinned"? And why did your "god" repent that he had made man on the earth? Looks to me like your "god" doesn't know everything.(And thus is NOT "omniscient.") It must be true. Your Bible tells us so.