The author uses this rhetorical question to emphasize that no one knows the character the man who will inherit his wealth. Alternate translation: "For no one knows whether he will be a wise man or a fool." (See: [[rc://en/ta/man/translate/figs-rquestion]])
This refers to things that are done on earth. See how you translated this in [Ecclesiastes 1:3](../01/03.md). Alternate translation: "on the earth" (See: [[rc://en/ta/man/translate/figs-idiom]])
Here the author's "work" and "wisdom" represent himself and the things he did in his wisdom. He probably had help with the literal buildings. Alternate translation: "that I worked very hard and wisely to build" (See: [[rc://en/ta/man/translate/figs-metonymy]])
The author speaks of useless and meaningless things as if they were mist.See how you translated this in [Ecclesiastes 1:14](../01/14.md). Alternate translation: "as uselessas vapor" or "meaningless" (See: [[rc://en/ta/man/translate/figs-metaphor]])