There are lots of facts you can find which help to persuade you that learning English is a good idea - 400 million first language speakers, 700 million second or foreign language speakers, over a billion people learning it right now!.
The result is that more and more every day, people expect you to know some English, and it's not only English speaking people who expect it - another fact often given is that 80% of the English used in the world is used between non-native speakers.
Learning to speak English well may be the best thing you can do to improve your life. That number doubles when people who speak English as a second or third language are counted.