Possible meanings are 1) just as salt makes food good, disciples of Jesus influence the people of the world so that they will be good. Alternate translation: "You are like salt for the people of the world" or 2) just as salt preserves food, disciples of Jesus keep people from becoming totally corrupt. Alternate translation: "As salt is for food, you are for the world" (See: [[rc://en/ta/man/translate/figs-metaphor]])
Possible meanings are 1) "if the salt has lost its power to do things that salt does" or 2) "if the salt has lost its flavor." (See: [[rc://en/ta/man/translate/figs-metaphor]])
"how can it be made useful again?" Jesus uses a question to teach the disciples. Alternate translation: "there is no way for it to become useful again." (See: [[rc://en/ta/man/translate/figs-rquestion]] and [[rc://en/ta/man/translate/figs-metaphor]])
This can be stated in active form. Alternate translation: "except for people to throw it out into the road and walk on it" (See: [[rc://en/ta/man/translate/figs-activepassive]])