See Party Missions for general overview of party missions. This party mission works in the same way as the normal Sharffenberger
mission. If you can't take on the mobs, move everybody to a mob-free area first (e.g. I7, E4).
Use a high DEF Rating fighter as a main tank to lure Sharffenberger
Fury Sharffenberger has high ATK Rating and has a high chance to inflict [Stun] status. This can be removed with Refresh Mind from [Tactical Assistance] stance. Likewise, [Fear] and [Ritardi] status can be removed with Recover from [Medic] stance.
If the main tank is having problems, allocate more fighters on both sides. If the main tank dies, the secondary tanks should spam Provoke skill. His DEF is relatively high, so you can bypass it with [Shock] status using lightning elementalists, or just use skills with [Ignore DEF] property.
Since this party mission is similar to the field raid version, see Wiki of the New World: Raids for more recommendations or tactics. See also クエスト/シャペンベルガーザカース 党.