Header Language and Header Currency
The language switcher is used for the WPML plugin https://wpml.org/. You need to purchase it. After installing the plugin, you will be able to add your languages in the plugin settings page. If you don't need this feature, you can disable it in Theme Options > Header tab. You find the Header Language option and disable it.
The currency switcher is used for the WooCommerce Multilingual plugin https://wordpress.org/plugins/woocommerce-multilingual/. This plugin needs the WPML plugin to work. You can also disable it in Theme Options > Header tab. Or you can install https://wordpress.org/plugins/woocommerce-currency-switcher/. It does not need WPML to work.