Unfortunately, the online document says, "The skills category is valid only for skills, not languages."
https://help.mypurecloud.com/articles/add-people-csv-file-import/
That said, You can use the bulk API for updating the users;
https://developer.dev-genesys.cloud/devapps/api-explorer#patch-api-v2-users--userId--routinglanguages-bulk
Att,
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Breno Canyggia Ferreira Marreco
https://www.linkedin.com/in/brenocfm-40b62182/------------------------------