Language: You can add your own local language and save it to the database. Following are the languages option given to edit and manage.
If you need to edit, the default language, then click on the language you want to edit and edit it as per your requirement.
You need to make sure, when you edit, you need to match other language IDs and edit those values as per your new edited value.
Language ID should match with other languages ID, else language phrase will be different. Manage it carefully.
Default site language can be set from basic settings.
If you want to add new local languages, we can support you and create new languages for you for free. Please contact us for the same.
Deleting option is not given as it could lead into site errors.
Multi-language option is only available for front end site and NOT for admin panel.