Add multiple tasks to a project

Hi all,
I have a problem to create multiple tasks to a project (to begin); I have this error at the end for example :
"error mesg Project: 'FR06STAD_SVG1';Task:'HS ACH.Amortissement-HS ACH.Amortissement'
Parent tasks must be specified before the child tasks."

My code is :

PROCEDURE DTEA_LOAD_REP_PJT_TSK(errbuf_ OUT VARCHAR2, retcode_ OUT NUMBER)
IS
    user_id_                        NUMBER;
    l_resp_id                       NUMBER;
    l_resp_appl_id                  NUMBER;
    rejection_group_id_             NUMBER;
    p_debug_flag                    CHAR := 'Y';
     
    l_date_deb_task                 DATE;
    l_date_fin_task                 DATE;
    l_cross_charge                  VARCHAR2(1);
    l_direct_flag                   VARCHAR2(1);