Hello @Zsofia_Kope ,
Since the same issue might belong to multiple sprints during the lifecycle, grouping of sprints might not work that well on the issue level.
You might group Sprints in the Sprint dimension using external data import. Please read more about that in the community post here - Aggregate Sprint By Name - #3 by zane.baranovska .
Regards,
Oskars / support@eazyBI.com