I think there are so many Japanese people who are not good at English. Why this happens? I suppose that they learned unnecessary English such as English for just entrance examination too much and they became to hate to learn English.
In Japanese junior high school, one of the first sentence to learn might be "This is a pen". But how many people use this sentence during real life? If there is pen in front of you, you don't have to explain that “This is a pen” because the person in front of you should know the pen if the person is not a primitive man.
When my kids entered elementary school in the US, the first words they learned were Pee & Poo and those words are highly necessary words for their school life.
In business world, English became international standard language, and if you can't use English, you can't execute your business well. I think the efficient way to improve your English ability is to put yourself in the necessary English environment for your life and business. This is the reason why I say, “The necessity is the mother of improvement”.