How to translate theme?
In order to translate the theme, please follow the next steps:
Theme's .pot file is located in /wp-content/themes/your-theme-name/languages folder.
Please use PoEdit - https://poedit.net/ to translate the .pot file and create respective .po and .mo files.
Please name .po and .mo files e.g. nl_NL.po and nl_NL.mo (nl_NL is the language code for dutch). For other languages' codes, please refer to the following link: Internationalization.
You should upload .po and .mo files created using PoEdit back to languages folder.
Also make sure to translate the theme's plugin, located in \wp-content\plugins\your-theme-name\languages folder.
The steps are the same as for the theme, except the files should be named bt_plugin-nl_NL.po and bt_plugin-nl_NL.mo (with appropriate language code).
You can set the site language of your WordPress installation on Settings > General. WordPress will automatically use the right language files if they exist.