en_tn_lite_do_not_use/ecc/02/22.md

For what profit does the person gain who works so hard and tries in his heart to complete his labors under the sun?

The author uses a rhetorical question to emphasize that the man who works hard gains nothing. Translate "what profit does ... gain" as you did in Ecclesiastes 1:3. Alternate translation: "For the person who works so hard and tries in his heart to complete his labors under the sun gains nothing." (See: rc://en/ta/man/translate/figs-rquestion)

works so hard and tries in his heart

These two phrases mean basically the same thing and emphasize how strenuously the person works. (See: rc://en/ta/man/translate/figs-parallelism)

tries in his heart

This is an idiom. Alternate translation: "tries anxiously" (See: rc://en/ta/man/translate/figs-idiom)

under the sun

This refers to things that are done on earth. See how you translated this in Ecclesiastes 1:3. Alternate translation: "on the earth" (See: rc://en/ta/man/translate/figs-idiom)