What you want is not possible with JPQL.
Group By do?
It combines all rows that are identical in the columns in the group by clause in to one row. Since it combines multiple rows into one, data in other columns can only be present in some combined fashion. For example, you can include MIN/MAX or AVG values, but never the orginal values.
Also the result with always be a table, never a tree.
Also note: there is no duplicated data. Every combination of secteur and agence appears exactly once.
If you want a tree structure, you have to write some java code for that.