ditban Not too sure about doing specific translations in WP however, after taking reference help from various tutorials like one from Gavick site and here , Have installed language file of yours as per the steps as seen in this tutorial
Also, The string translation can be seen here which has been done through Loco translate plugin installed
Try to clear your browser cache to see the same is reflecting fine on your site
You may also contact the developer of specific plugin if the translation doesnt reflect as I might be missing some step thereon