I see. The default language in Configuration\Translations is which language is set for new users you create. This will not effect you helpdesk language.
The Translations below are so that you can edit/create new translations. The "Enabled" button is to allow helpdesk users to select it as their helpdesk language.
To select your helpdesk language you need to use the blue cog in the top right-hand corner and select the correct language there.