Folks say any time certain age, it's just impossible to enhance pronunciation of one's second names. Practice is one of the many ways to find you speaking. Listen for an hour, then read a novel a good hour. http://ayudas.invemar.org.co/web/thehuan/home/-/blogs/10-trung-tam-tieng-anh-giao-tiep-a-nang-uy-tin-nhat