Hi,
I would say that the best way to copy a complete site is to use
export/import feature of Kentico CMS (
http://devnet.kentico.com/docs/5_5r2/devguide/index.html?export_and_import_overview.htm) where you will export your website
and import it under diffrent name as your current website into the Kentico CMS
instalation.
Regrettably, the functionality of translating multiple pages is not provided
in your version of Kentico CMS. You can change culture for all existing documents
in Site Manager/Sites, in default culture dialog, but not translate then all into
a new culture version. You need to do it manually.
Best Regards,
Roman Konicek