Divi & Polylang have a weird bug when you have both installed on the same website: no matter what your user account has selected as its preferred language, Divi's backend builder will always show the translation for the primary language set in Polylang.

Set Divi's Backend to English even with Polylang installed

#region Set Divi's backend to English for Oli's user account
add_filter( 'load_textdomain_mofile', 'switch_divi_to_en', 10, 2 );
/*
 * Replace 'textdomain' with your plugin's textdomain. e.g. 'hello-dolly'. 
 * Define your filename, such as: yourtranslationfile-en_GB.mo
 * Define the location, for example: wp-content/languages/textdomain/yourtranslationfile-en_GB.mo
 */
function switch_divi_to_en( $mofile, $domain ) {
	if ( $domain === 'et_builder' && get_current_user_id() == 9) {
		$mofile = get_template_directory() . '/includes/builder/languages/en_US.mo';
	}
	return $mofile;
}
#endregion Set Divi's backend to English for Oli's user account