The author uses a rhetorical question to cause the reader to think deeply about important things. Translate "what profit does a man gain from all the work" as you did in [Ecclesiastes 1:3](../01/03.md). Alternate translation: "A man seems to gain no lasting benefit from all the work and from the striving of heart that he labors at under the sun." (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]])