Learning Spoken English . . . in half the time

You have an opportunity for a better paying job, but you need to improve your English before you can apply. Or, you want to enroll in a university in the United States, but your English is not good enough yet.
You have already taken English classes for two years in secondary school. Maybe you have studied more English at the university. You know English grammar and can write, but you need to learn how to speak English.