This speaks of how everything in life vanishes and has no lasting value as if everything were like a disappearing vapor or breeze. AT: "Like a vapor of mist vanishes and like a breeze in the wind disappears, everything vanishes and has no lasting value" (See: [[rc://en/ta/man/translate/figs-simile]])
The author uses this rhetorical question to emphasize that man's work is pointless and has no lasting benefit. This question can be written as a statement. AT: "Mankind gains no profit ... under the sun." (See: [[rc://en/ta/man/translate/figs-rquestion]])