Joining Table with Itself MYSQL - mysql

Question

I have a scenario where i have table app_users in which i am storing multiple types of users , and each user have different column for phone number , and Names , i am trying to get phone number and name of specific type of user , it's hard to understand this way , but see the working example Query below :
SET #sk := (SELECT app_users.skeeper_phone as sphone FROM app_users WHERE app_users. app_user_type = 'SKEEPER' LIMIT 1);
SELECT
acs.id as complainId,
IF(
(#sk) > 0,
#sk,
''
) as sk_phone,
(
SELECT
IF(
auu.institute_phone IS NULL,
auu.department_phone,
auu.institute_phone
) as cphone
FROM app_users as auu
WHERE auu.id = acs.app_customer_id
LIMIT 1
) as cphone,
(
SELECT auuu.other_user_phone as ephone
FROM app_users as auuu,app_admin_assign_eng as aase
WHERE aase.app_complain_service_id = acs.id AND auuu.id = aase.engineer_id
LIMIT 1
) as ephone,
(
SELECT auuu.fullname as ename
FROM app_users as auuu,app_admin_assign_eng as aase
WHERE aase.app_complain_service_id = acs.id AND auuu.id = aase.engineer_id
LIMIT 1
) as ename,
(
SELECT auuu.other_user_phone as ephone
FROM app_users as auuu,app_admin_assign_eng as aase
WHERE aase.app_complain_service_id = acs.id AND auuu.id = aase.admin_id
LIMIT 1
) as aphone
FROM app_complain_services as acs,app_users as au
WHERE
acs.id = 5
GROUP BY acs.id
Above query is working alright , but it is not optimized , what could be optimization and other ways to solve similar problem?