I learn English by learning vocabulary by topic. After memorizing the vocabulary, find ways to make sentences related to the learned vocabulary. Practice speaking a lot, learn through movies, music. practice thinking in English instead of thinking in Vietnamese translated into English. Reasons for learning is English is the most common language in the world,English opens up many opportunities,English makes  more attractive in the eyes of employers,English makes it easy for me to watch movies, give me rich knowledge. When traveling, I won't need to worry about getting lost in a foreign country, confidently ordering food and being able to chat with locals about their lives. English gives me more options to work in industries that require employees to be fluent in this language such as aviation, tourism, movies...