sorting some column of an internal table that meet a condition

I have an internal table

and i want to display it like this:

.

note that only a1's date is sorted descending. so im wondering if theres a method to only sort dates belong to a1 while leaving the others untouched.

I am a beginner so id appreciate if the answer is easy to understand

You can use the LOOP/GROUP approach to sort the table before sending it to the ALV (sample code only):

    LOOP AT itab ASSIGNING FIELD-SYMBOL(<line>)
                     GROUP BY ( key1 = <line>-cust_id key2 = <line>-prod_id ) ASCENDINGdd
                     ASSIGNING FIELD-SYMBOL(<grp1>).

          LOOP AT GROUP <grp1> ASSIGNING FIELD-SYMBOL(<member>).
            members = VALUE #( BASE members ( <member> ) ).
          ENDLOOP.

          IF <grp1>-prod_id = 'A1'.
            SORT members BY sale_date DESCENDING.
          ELSE.
            SORT members BY sale_date ASCENDING.
          ENDIF.

        APPEND LINES OF members TO it_final.
    ENDLOOP.

• First loop: sort ascending by cust_id/prod_id.
• Second loop: obtain all members of group and sorting as you like, then append to final table.

Reference: https://help.sap.com/doc/abapdocu_latest_index_htm/latest/en-US/index.htm?file=abaploop_at_itab_group_by.htm