You already set the language code to a website via advanced settings, but you don't translate for instance days with this information.

So if you use a CMS element as date, you still get "Thursday", even if you change the local of the site. And you have no option to translate this yourself, unless you add a custom script.

You could make a translation sheet for all your data, such as days, form field pre-text etc. and get the community to translate and vote for the correct translation. Just like Facebook did in the beginning.