The performance of the query can be achieved by removing the dependent subquery (which is executed for each row) so try this:
SELECT
`cs`.sku ,
group_concat(
IF(
tmp.za_count = 2,
`ccg`.name_en,
NULL
)
) as level_1_categories
FROM
catalog_simple `cs`
LEFT JOIN `catalog_config` `cc`
ON `cs`.`fk_catalog_config` = `cc`.`id_catalog_config`
LEFT JOIN `catalog_config_has_catalog_category` `cchcc`
ON `cc`.`id_catalog_config` = `cchcc`.`fk_catalog_config`
LEFT JOIN (
SELECT
`ccg`.`id_catalog_category`,
SUM(IF(`ccg1`.`id_catalog_category` IS NULL,0,1)) as za_count
FROM `catalog_category` `ccg`
ON `cchcc`.`fk_catalog_category` = `ccg`.`id_catalog_category`
LEFT JOIN `catalog_category` `ccg1`
ON `ccg1`.lft <= `ccg`.lft
AND `ccg1`.rgt >= `ccg`.rgt
GROUP BY
`ccg`.`id_catalog_category`
) as tmp
ON tmp.id_catalog_category = `cchcc`.`fk_catalog_category`
group by `cc`.sku