Possible meanings are 1) just as salt makes food good, a disciple of Jesus must influence the people of the world so that they will be good. AT: "You are like salt for the people of the world" or 2) just as salt preserves food, a disciple of Jesus must keep people from becoming totally corrupt. AT: "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. AT: "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. AT: "except for people to throw it out into the road and walk on it" (See: [[rc://en/ta/man/translate/figs-activepassive]])
This means Jesus' followers bring the message of God's truth to all the people who do not know God. AT: "You are like a light for the people of the world" (See: [[rc://en/ta/man/translate/figs-metaphor]])
At night when it is dark, people can see the city lights shining. This can be stated in active form. AT: "During the night, no one can hide the lights that shine from a city on a hill" or "Everyone sees the lights of a city on a hill" (See: [[rc://en/ta/man/translate/figs-explicit]] and [[rc://en/ta/man/translate/figs-activepassive]])