We recommend using Loco Translate plugin to translate your website into your language.
You can download it at https://wordpress.org/plugins/loco-translate/

This theme comes with .pot file for the theme, it is located in the \oswald\languages\ folder.
Please follow these steps to translate your theme text:

Step 1 – please download this software and install it http://www.poedit.net/download.php;
Step 2 – please open .pot or .po files located in \oswald\languages\oswald.pot using poedit tool and translate the existing text to your own;
Step 3 – when you save the file, you must name it according to your language;
Step 4 – upload the file to the required folder on your server, that’s all.

Please note that you can also use the special plugins like WPML to have a multilanguage website.