'Really' in the Bible

Who really knows if the human spirit ascends upward, and the animal's spirit descends into the earth?

So do the wise [really] have an advantage over fools? {Can the poor [really] gain anything by knowing how to act in front of others}?

Who is really wise? Who knows how to interpret this saying: "A person's wisdom improves his appearance, softening a harsh countenance."

then I discerned all that God has done: No one really comprehends what happens on earth. Despite all human efforts to discover it, no one can ever grasp it. Even if a wise person claimed that he understood, he would not really comprehend it.