SELECT 
  lang.name, 
  IF(
    cscart_ult_language_values.value IS NULL, 
    lang.value, cscart_ult_language_values.value
  ) as value 
FROM 
  cscart_language_values lang 
  LEFT JOIN cscart_ult_language_values ON cscart_ult_language_values.name = lang.name 
  AND company_id = 1 
  AND cscart_ult_language_values.lang_code = lang.lang_code 
WHERE 
  lang.lang_code = 'en' 
  AND lang.name IN (
    'text_combination_out_of_stock', 
    'sku', 'select_options', 'notify_when_back_in_stock', 
    'enter_email', 'enter_email', 'go', 
    'old_price', 'list_price', 'enter_your_price', 
    'sign_in_to_view_price', 'inc_tax', 
    'including_tax', 'you_save', 'you_save', 
    'save_discount', 'availability', 
    'in_stock', 'availability', 'in_stock', 
    'availability', 'qty', 'text_cart_min_qty', 
    'text_edp_product', 'text_combination_out_of_stock', 
    'sku', 'select_options', 'notify_when_back_in_stock', 
    'enter_email', 'enter_email', 'go', 
    'old_price', 'list_price', 'enter_your_price', 
    'sign_in_to_view_price', 'inc_tax', 
    'including_tax', 'you_save', 'you_save', 
    'save_discount', 'availability', 
    'in_stock', 'availability', 'in_stock', 
    'availability', 'qty', 'text_cart_min_qty', 
    'text_edp_product'
  )

Query time 0.00065

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "table_name": "cscart_ult_language_values",
      "access_type": "system",
      "possible_keys": ["PRIMARY"],
      "rows": 0,
      "filtered": 0,
      "const_row_not_found": true
    },
    "table": {
      "table_name": "lang",
      "access_type": "range",
      "possible_keys": ["PRIMARY"],
      "key": "PRIMARY",
      "key_length": "392",
      "used_key_parts": ["lang_code", "name"],
      "rows": 19,
      "filtered": 100,
      "attached_condition": "lang.lang_code = 'en' and lang.`name` in ('text_combination_out_of_stock','sku','select_options','notify_when_back_in_stock','enter_email','enter_email','go','old_price','list_price','enter_your_price','sign_in_to_view_price','inc_tax','including_tax','you_save','you_save','save_discount','availability','in_stock','availability','in_stock','availability','qty','text_cart_min_qty','text_edp_product','text_combination_out_of_stock','sku','select_options','notify_when_back_in_stock','enter_email','enter_email','go','old_price','list_price','enter_your_price','sign_in_to_view_price','inc_tax','including_tax','you_save','you_save','save_discount','availability','in_stock','availability','in_stock','availability','qty','text_cart_min_qty','text_edp_product')"
    }
  }
}

Result