Future time is spoken of as if the "days are coming" And, here the word "darkness" refers to death. Alternate translation: "how many days that he will be dead" (See: [[rc://en/ta/man/translate/figs-metaphor]] and [[rc://en/ta/man/translate/figs-euphemism]])
Here the word "they" refers to the "days of darkness" Alternate translation: "for he will be dead for many more days than he is alive" or "for he will be dead forever"
Here "vanishing vapor" is a metaphor. Possible meanings are 1) Alternate translation: "No one knows what will happen after he dies" or 2) Alternate translation: "Everything to come is meaningless" (See: [[rc://en/ta/man/translate/figs-metaphor]])