This begins the story of Philip, whom the people had chosen as a deacon. (See: Acts 6:5)
The cause for the scattering, the persecution, was stated previously. This can be stated in active form. AT: "who had fled the great persecution and had gone" (See: rc://en/ta/man/translate/figs-activepassive)
"Word" here is a metonym for "message." AT: "proclaiming the message from God" (See: rc://en/ta/man/translate/figs-metonymy)
The phrase "went down" is used here because Samaria is lower in elevation than Jerusalem.
Possible meanings are 1) Luke expected the readers to know which city he was writing about. AT: "the main city in Samaria" or 2) Luke did not expect his readers to know which city he was writing about. AT: "a city in Samaria"
The title "Christ" refers to Jesus, the Messiah. AT: "told them that Jesus is the Messiah" (See: rc://en/ta/man/translate/figs-metonymy)