en_tn_condensed/ecc/02/19.md

For who knows whether he will be a wise man or a fool?

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)

he will be

The word "he" refers to the author's heir.

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)

that my work and wisdom have built

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)