This is a hypothetical situation about what two people might be doing at the time. It can be translated as "there may be two men on one couch." (See: [[rc://en/ta/man/translate/figs-hypo]])
"one man will be taken and the other man will be left behind." AT: "God will take one man and leave the other," or "angels will take one and leave behind the other." (See: [[rc://en/ta/man/translate/figs-activepassive]])
This is a hypothetical situation about what two women might be doing at the time. AT: "there may be two women grinding grain together." (See: [[rc://en/ta/man/translate/figs-hypo]])
Apparently this is a proverb that means "It will be obvious" or "You will know it when it happens." It can also be translated as a simile: "As vultures gathering shows that there is a dead body, so these things show that the Son of Man is being revealed." (See: [[rc://en/tw/dict/bible/other/proverb]], [[rc://en/ta/man/translate/figs-simile]])
Vultures are large birds that fly together and eat the flesh of dead animals that they find. You could describe birds this way or use the word for a local bird that does this.