Complex sentence: The player hosting the session is able to keep the progress data after multiplayer is finished and can continue the story onwards, however the other players will find themselves back where they started in their own games only with the additional stats and items gained while playing multiplayer.
Split into simpler sentences: The player hosting the session is able to keep the progress data after multiplayer is finished and can continue the story onwards. However the other players will find themselves back where they started in their own games only with the additional stats and items gained while playing multiplayer.