[girigiri]

Not English, nor any other language.

Language can only be properly learnt through interaction with other people. A study group with members having about the same skills and with very good teaching materials might be able to succeed. But studying alone will only have limited benefit.

If you look around this site and others, you will note that people with English as a second language and with highly developed skills are actively seeking advice on how to improve. They are taking as their teachers, native speakers of English. They also spend time using English as best they can to communicate with other people.

The same approach is used for learning Japanese (and a variety of other languages). Learning a language and learning about a language are two very different processes.