Hi Maxglo,
Thank you for your purchase.

You can change language on wpDataTables settings page, but it uses only the core Datatables localization, which means, only the strings in front-end related to basic functionality (global search, pagination, info) are translated.

If you want to translate admin section of plugin and everything else you can take a look at this post from our website - http://wpdatatables.com/wpdatatables-localization-translation/