"Word of man" here is a synecdoche for "a message that comes simply from a man." AT: "(it is) not a message that is made up by a man" (See: [[rc://en/ta/man/translate/figs-synecdoche]]).
"Word" here is a metonym for "message." AT: "you received it as it truth is, the message that comes from God" (See: [[rc://en/ta/man/translate/figs-metonymy]])
Paul speaks of God's gospel message as if it were a person who was doing work. "Word" is a metonym for "message." AT: "It is this set of God's instructions that enables those of you who believe to work well together" (See: [[rc://en/ta/man/translate/figs-personification]] and [[rc://en/ta/man/translate/figs-metonymy]])