he who is greatest among you

"the person who is most important among you"

among you

Here "you" is plural and refers to Jesus' followers. (See: rc://en/ta/man/translate/figs-you)

"makes himself important"

This can be stated in active form. AT: "God will humble" (See: rc://en/ta/man/translate/figs-activepassive)

This can be stated in active form. AT: "God will make important" or "God will honor" (See: rc://en/ta/man/translate/figs-activepassive)