You can choose to install SuperOffice CRM in one or more languages.
In a new installation, only the main language is used for most of translated texts that are installed in the database. This will remain the same even if you install with several languages, and later select to run SuperOffice CRM in another language than the main language. This will cause some of the text in the application to be in the main language and most in the selected language. (Seen in dropdown lists for example.)
If you are upgrading from an earlier version of SuperOffice, make sure to select the same main language as in last installation, or you risk getting a mix of languages in the database/program.