“pointless.” See commentary on Ecclesiastes 1:2. Here we see the meaning of “temporary” take on some more significance. The life is temporary, and given the context, “pointless.”
“he makes like a shadow.” The subject is unclear. Does a person make his life like a shadow, passing quickly and not well remembered, or does God (getting the subject from Ecc. 6:10) make a person’s life like a shadow? It may well be both and is left unclear for our consideration.
“will be after him.” In Hebrew, the future is generally “after” a person, also, it is said to be “behind” them in the sense that it cannot be seen (cp. Ecc. 3:22; 7:14).