SQL & PL/SQL

CREATE TABLE new_details_staging (
    e_id         NUMBER(10),
    e_name       VARCHAR2(30),
    portal_desc  VARCHAR2(50),
    risk_dec varchar2(50),
    CONSTRAINT pk_new_details_staging PRIMARY KEY ( e_id )
);

INSERT INTO new_details_staging VALUES (
    11,
    'A',
    'AA',
    'High'
);

INSERT INTO new_details_staging VALUES (
    22,
    'B',
    'BB',
    'Low'
);

CREATE TABLE lookup_ref (
    ref_id        NUMBER(10),
    ref_typ       VARCHAR2(30),
    ref_typ_desc  varchar2(20),
    CONSTRAINT pk_lookup_ref PRIMARY KEY ( ref_id )
);

INSERT INTO lookup_ref VALUES (
    181,
    'portal',
    'AA'
);

INSERT INTO lookup_ref VALUES (
    182,
    'portal',
    'BB'
);

INSERT INTO lookup_ref VALUES (
    183,
    'risk',
    'High'
);

INSERT INTO lookup_ref VALUES (
    184,
    'risk',
    'Low'
);

   CREATE TABLE new_details_main (
    e_id    NUMBER(10),
    e_name  VARCHAR2(30),
    portal  NUMBER(20),
    risk number(20),
    CONSTRAINT pk_new_details_main PRIMARY KEY ( e_id )
);

commit;

My Attempt :

INSERT INTO new_details_main (e_id, e_name, portal,risk)
SELECT  n.e_id
,   n.e_name
,   (
      SELECT  lr.ref_id
      FROM    lookup_ref lr
      WHERE   lr.ref_typ        = 'portal'
      AND     lr.ref_typ_desc   = n.portal_desc
    ),
    (
      SELECT  lr.ref_id
      FROM    lookup_ref lr
      WHERE   lr.ref_typ        = 'risk'
      AND     lr.ref_typ_desc   = n.risk_dec
    )
    
FROM    new_details_staging n
;

Currently, I am inserting a few records and it is giving exact results but in actuality, there are 40k+ records so I believe it will give performance issues also. Is there any way to insert the records faster because I will write a procedure for this insertion? Is there any other in which I can write an insert query inside the procedure?