Content Management System for multilingual website

I'm designing a CMS in which expert users will be able to publish their own content and I want them to be able to add the same content in different languages. (We want expert users to manage themselves the different languages of their own content while we manage the langages of everything else on the website)

Should expert users manage their content by language and create a content in each different language OR should they manage all of their content at the same time and then specify the different languages in the content itself ?

If you have another way to do it I'd also be glad to read it.