Polite: showing good manners toward others, as in behavior, speech, etc.; courteous; civil: Friendly means acting in a non-threatening manner toward and/or showing kindness to someone, as a friend would behave. Thus friendly implies a mode of friendship as distinct from amiable or genial. Professional service is expected to be amiable or genial but not necessarily friendly.

friendly = 友情 polite = 客气 Use a dictionary!