Currently, there exist no localization support for the Graph API. The Graph API will return only in the language the data is stored in Azure Active Directory. There is no way to return any other language other than English, as the data stored in Azure AD is English language.
Usually the logic is, graph API pulls the response from Azure active directory, and it should translate the response in users preferred language.
At present graph API doesn't support language translations for response that it gets from Azure AD.
It might be planned for future, but we do not have any ETA on that. You can track the features of graph API in https://developer.microsoft.com/en-us/graph/changelog/?search=
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