Group quests are intended for all union members. Completing them is not easy because they are designed as a challenge for the union as a whole, but the rewards are totally worth it.
Each group quest requires unions to accomplish a certain objective in a limited amount of time. You can see what the objective is in the name of the quest, in the notes under the progress bar, or by pressing the quest icon and reading the full info.
If the quest is completed on time, both the union and its members will receive points and rewards. The participants will receive points for both completing the quest and carrying out certain actions during the quest. The exact number of received points can be seen in the notes.
Some quests also provide a quick access button that allows players to instantly find the quest’s objective.

The points for your achievements in the union quests should be counted on the leaderboard within a few hours if you are playing with a stable Internet connection.