With Cinema 4D S24 we change the way to add an additional language.
You now can install the language directly from within the Preferences of Cinema 4D (use "Ctrl/Cmd + E" or the menu "Edit/Preferences").
Go to "Interface" and click on the little arrow in front of "Language".
Clicking on "Install Language..." you receive a list of the available languages and you can install the one you want to use.
Note: You need an active internet connection to download and install language files.