Translating strings from HTML

Hello. Thank you for plugin.
We use a link to the MultivendorX plugin, and my navigation and page title (inside the plugin dashboard) aren’t translated. Is there a way to translate the string Messages %s?

Messages <span class="%s">%s</span>

I tried that.

function custom_better_messages_force_translation( $translated_text, $text, $domain ) {
    if ( $domain === 'bp-better-messages' && $text === 'Messages <span class="%s">%s</span>' ) {
        $translated_text = 'Zpravy <span class="%s">%s</span>';
    }
    return $translated_text;
}
add_filter( 'gettext', 'custom_better_messages_force_translation', 20, 3 );

But it didn’t help. The Loco Translate plugin (Individual) is used for translation. If there’s a solution, could you please share it? We use the Ajax version.