Correct my sentences, please. I understand what he wants to say. But it is not adapted to the student who has no chance to listen to the target language in his/her daily life and the student has already got a wrong(not standard) accent. And a child and an adult are different. Human beings have a thing called “language formative years”. It is a time that we can naturally learn a language. It is from 3 years old to 13 years old. Once we become older than 13 years old, we need to study and learn by using materials(textbooks, teachers etc.) intentionally. He said to me that he studied Japanese grammar by using a free site. Then he can/should study Japanese accent and accent rules by using materials. That is an efficient learning method. ※He wrote ありがとう at the end of the comment. But he should not write it. To say ありがとう is strange because you haven't known whether someone gives you a favor. It might be a correct expression in English. But in Japanese, we don't say "ありがとうThank you" before we know someone gives us a favor.