Make this query run fast

I used Database Engine Tunning Advisor for create some statistic and index but still run long so i this something should be changed in the way is write

  
  SELECT
              C.code_commande AS 'Order',
              C.code_client AS 'Cust&#46',
              CL.nom_fac_client AS 'Cust&#46 Name',
              LTRIM(RTRIM(C.code_commande_client)) AS 'Cust&#46 Ref&#46',
              C.total_quantite_commande AS 'Qty',
              C.code_devise AS 'Curr&#46',
              CONVERT(VARCHAR,sum(LC.quantite_commandee*LC.prix_net_unit_ligne_commande)) AS 'Price',
              CONVERT(VARCHAR,C.date_commande_client,23) AS 'Order Date',
              VCS.libelle_statut AS 'Status',
              'Seller' = (P.nom_personne +' '+ P.prenom_personne),
              ISNULL(EC.Vehicule,'') 'Container',
              CI.code_incoterm AS 'Incoterm',
              X.xlatlongname AS 'Shipment',
              VLF.code_facture AS 'inf_invoiceId', 
              CONVERT(VARCHAR,VLF.date_facture,23) AS 'inf_invoiceDate',
              CASE 
                 WHEN (VCS.code_statut = 'A' AND VCS.code_type_traitement = 'D') THEN '1'
                 ELSE '0'
              END AS 'inf_approvedButDelayed',
              CASE 
                 WHEN (VCS.ordre between 4 and 13 and C.total_quantite_commande > 0)
                       OR (VCS.code_statut = 'O' and C.total_quantite_commande < 0 ) THEN '1'
                    ELSE '0'
              END AS 'inf_soRef',
              inf_company = 'G CORP',
              ISNULL(CL.bloque_client, '0') AS 'inf_bloqueCompta'
  
           FROM COMMANDE C
           LEFT JOIN CLIENT CL ON CL.code_client = C.code_client
           LEFT JOIN FILIALE_VENTE FV ON FV.code_filiale_vente = CL.code_filiale_vente
           LEFT JOIN REGION_VENTE RV ON RV.code_region_vente = FV.code_region_vente
           LEFT JOIN LIGNE_COMMANDE LC ON LC.code_commande = C.code_commande
           LEFT JOIN PERSONNE P ON P.code_vendeur = C.code_vendeur_commande
           LEFT JOIN 
              (SELECT 
                 CS.code_commande,
                 SC.libelle_statut,
                 CS.code_statut,
                 CS.code_type_traitement,
                 SC.ordre 
              FROM STATUT_COMMANDE SC, COMMANDE_STATUT CS
              WHERE CS.CODE_STATUT=SC.CODE_STATUT ) VCS ON C.code_commande = VCS.code_commande
           LEFT JOIN 
              (SELECT DISTINCT 
                 F.CODE_FACTURE, 
                 F.DATE_FACTURE,
                 LF.CODE_COMMANDE_FACTUREE 
              FROM FACTURE F, LIGNE_FACTURE LF
              WHERE F.CODE_FACTURE = LF.CODE_FACTURE
                 AND F.DATE_FACTURE = LF.DATE_FACTURE
                 AND F.CODE_CLIENT <>419124
                 AND LF.CODE_COMMANDE_FACTUREE is not null ) AS vLF ON vLF.CODE_COMMANDE_FACTUREE=C.CODE_COMMANDE
  
           LEFT JOIN COMMANDE_INFOS CI ON CI.CODE_COMMANDE=C.CODE_COMMANDE
           LEFT JOIN MOD1_EXPEDITION_COMMANDE MEC ON MEC.code_commande = C.code_commande
           LEFT JOIN ENVOI_CAMION EC ON EC.num_envoi = MEC.numero_expedition AND EC.num_camion = 1
           LEFT JOIN XLATTABLE X ON X.FIELDNAME = 'Type_Livraison' and X.FIELDVALUE = isnull(CI.CODE_TYPE_LIVRAISON_ADV, CI.CODE_TYPE_LIVRAISON)
           LEFT JOIN PERSONNE_VENTE PV ON PV.code_personne = 817	
           LEFT JOIN VPFL_PERSONNE_PAYS VPFL ON VPFL.code_personne = PV.code_personne
  
           WHERE
              C.CODE_COMMANDE > 1000000
              AND EXISTS(SELECT LC.code_commande FROM LIGNE_COMMANDE LC WHERE LC.code_commande = C.code_commande)
  			   AND C.total_quantite_commande IS NOT NULL 
              AND C.CODE_VENDEUR_COMMANDE <>99
              AND C.CODE_VENDEUR_COMMANDE=P.CODE_VENDEUR
              AND C.CODE_COMMANDE=LC.CODE_COMMANDE
              AND C.CODE_CLIENT=CL.CODE_CLIENT
              AND PV.code_personne = 817
              /* ------------ Restriction filiale vente et zone géographique -------------*/
              AND ((CL.code_filiale_vente = PV.code_filiale_vente) OR (ISNULL(CL.code_filiale_vente, '0') = 0))
              AND CL.code_pays_fac = VPFL.code_pays
  
           GROUP BY 
              C.code_commande,
              C.code_client,
              CL.nom_fac_client,
              C.code_commande_client,
              C.total_quantite_commande,
              C.code_devise,
              C.date_commande_client,
              P.nom_personne,
  			      P.prenom_personne,
              VCS.libelle_statut,
              VLF.code_facture,
              VLF.date_facture,
              VCS.ordre,
  			      VCS.code_statut,
              VCS.code_type_traitement,
              EC.Vehicule,
              CI.code_incoterm,
              X.xlatlongname,
              CL.bloque_client
           ORDER BY C.code_commande desc,
                    C.code_client desc

thank you

This is just from reviewing the query. I have no idea of volume, setup, size, indexes, execution plan or anything. DDL and sample data would be helpful

1) IsNull operation on join column
     LEFT JOIN XLATTABLE X ON X.FIELDNAME = 'Type_Livraison' 
	  and X.FIELDVALUE = isnull(CI.CODE_TYPE_LIVRAISON_ADV, CI.CODE_TYPE_LIVRAISON)

2) Not sure what this is for
      LEFT JOIN PERSONNE_VENTE PV ON PV.code_personne = 817	

3) And exists causes rebar
    AND EXISTS(SELECT LC.code_commande FROM LIGNE_COMMANDE LC WHERE LC.code_commande = C.code_commande)
  
4) this is there twice
	AND PV.code_personne = 817
 
5) or statement will slow things down quite a bit
     AND ((CL.code_filiale_vente = PV.code_filiale_vente) OR (ISNULL(CL.code_filiale_vente, '0') = 0))
 
6) <> is not good
  (SELECT DISTINCT 
		 F.CODE_FACTURE, 
		 F.DATE_FACTURE,
		 LF.CODE_COMMANDE_FACTUREE 
	  FROM FACTURE F, LIGNE_FACTURE LF
	  WHERE F.CODE_FACTURE = LF.CODE_FACTURE
		 AND F.DATE_FACTURE = LF.DATE_FACTURE
		 AND F.CODE_CLIENT <>419124
		 AND LF.CODE_COMMANDE_FACTUREE is not null ) AS vLF ON vLF.CODE_COMMANDE_FACTUREE=C.CODE_COMMANDE

7) Old/Deprecated join
	  (SELECT 
		 CS.code_commande,
		 SC.libelle_statut,
		 CS.code_statut,
		 CS.code_type_traitement,
		 SC.ordre 
	  FROM STATUT_COMMANDE SC, COMMANDE_STATUT CS
	  WHERE CS.CODE_STATUT=SC.CODE_STATUT ) VCS ON C.code_commande = VCS.code_commande