A good WordPress language translator as recommend by Neil Patel is Transposh click here.
Mandarin and Spanish are the worlds most popular languages with English 3rd http://www.alsintl.com/blog/most-common-languages/
Getting the new pages into your sitemap
French version /fr/
Hindi version /hi/
Example language SEO from wego.com header on the arabic version – notice all versions of English are specified en, en-sg, en-au, en-ca etc.