Preparation is one matter, business English improvement is another.
Preparation will allow the release of your full knowledge at the time of the test by becoming accustomed to the test environment. In this way you could possibly achieve a higher score. Naturally any contact with English will lead to an improvement in knowledge, but the use of preparation for improvement is a little like trying to fill your swimming pool with water using a teaspoon.
Business English improvement will improve your knowledge and ability to use English both quickly and efficiently. Business English improvement includes much more than just learning grammar and vocabulary, it also means improving your ability to understand and ability to locate information in both the spoken and written forms, to feel the music of the language. Good business English training is vital to generally improve your use of English.