Ok, the title sounds pretentious. But everyone has a reason to write. My reason to write 20 Mandarin textbooks, to put up with the pain and the long hours, are stated below.
Many people start learning Mandarin after they have started their career. For them, time is precious. But often, half of the time they spend on learning Mandarin is wasted. They often spend too much time trying to remember the tones, and lose the opportunity to do focused practice.