Am I sinful for downloading episodes of the series "Hareem Al-Sultan" for a friend of mine?

You are not permitted to download episodes of TV series that contain forbidden elements, such as images of women and music, for your friend. This is because doing so constitutes assisting in the viewing of objectionable content. Allah Almighty says: "And do not cooperate in sin and aggression." Whoever assists in a sin is a partner to its doer in the transgression.