If you develop an application that's internationalized and localized, you can read the current display language for the authenticated user from his account entity. If an authenticated user switches the display language of your application you also should provide this change to his account.
https://api.cardmarket.com/ws/v1.1/account/language/:idLanguage
idLanguage
1
: English2
: French3
: German4
: Spanish5
: ItalianGET https://api.cardmarket.com/ws/v1.1/account/language/1
GET https://api.cardmarket.com/ws/v1.1/account/language/3