I am a Master's student at Stockholm University. I am from Bangladesh. I speak Bengali back home. English is my 2nd language. I am fluent in English. If we spend time on it on a regular basis, English is not hard to learn for a non-native speaker. If I can learn it anybody can. I found out that you learn more if you enjoy the process. It can be different for everybody. For me, it was music and movies, and TV shows. It can also be done by reading books.
For non-native speakers, it can be a little difficult, but not impossible.
Four to six months perhaps.
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