Thank you, I found another solution.
ClearCollect(
achievementsCollection,
GroupBy(
Achievement_Table,
"Week_x0020_of",
"Employee",
"AchievementGrouped"
)
);
ClearCollect(
plannedWorksCollection,
GroupBy(
PlannedWork_Table,
"Week_x0020_of",
"Employee",
"PlannedWorkGrouped"
)
);
To merge/link these 2 tables, I use AddColumns and LookUp
ClearCollect(GoodNewsCollection,AddColumns(achievementsCollection,"PlannedWorkGrouped",LookUp(plannedWorksCollection, Employee=achievementsCollection[@Employee] And Week_x0020_of=achievementsCollection[@Week_x0020_of],PlannedWorkGrouped)))
;