The interface language is a personal preference. Open the main menu, select My information, then General, choose the desired language, and save. Reload Nonli if the navigation does not update immediately.
Changing this preference translates the interface; it does not translate post content, article metadata, themes, or bot messages. Personal themes can also be scoped to the language in which they were created, so a theme may no longer appear after a language change even though it has not been deleted. Switch back to the original language to verify it.
If the setting returns to its previous value, save again and sign out, then sign back in. If several people use Nonli, each person should update their own user profile rather than sharing one account.