Learning how to speak English as a native speaker is quite hard for Vietnamese students while they are at high school. The approach to the basic pronunciation is limited at school which makes them miserable while communicating with a foreigner in English successfully.
I have had a great opportunity to closely work with numerous English-speaking people from various continents. Thanks to the job I did, I could finally master all the based sounds in English and that is the reason why I love to share my own experience with the younger generation...