There are many people in Japan that have lived for many years but never got around to properly learning the language. Also many people overseas interested in Japan. For all of you it would be very useful to reach a good Japanese level, it can help you unlock the next level in your career or personal relationship.
For those that identify with the above, check out this website https://www.carloscoordinator.com/ Carlos uses a method based on the research performed during his PHD, so that you can study and learn more efficiently. If you do not follow the correct method you may spend years and thousands of hours without much to show off, so be sure to check his free level test. There are also many interesting tips on his youtube channel with I encourage you check by yourself: https://www.youtube.com/c/CarlosCoordinator
