My knowledge of Japanese is rather poor.

Source: Tatoeba

I don't know anything about Japan.

Source: Tatoeba

I don't know much about Japan.

Source: Tatoeba

I am interested in Japanese history.

Source: Tatoeba

He has only a superficial knowledge of Japanese.

Source: Tatoeba

Are you interested in Japanese music?

Source: Tatoeba

He is very much interested in Japanese history.

Source: Tatoeba

Mary has an interest in Japanese language and history.

Source: Tatoeba

He is very much interested in Japanese history. We are surprised at his vast knowledge of the subject.

Source: Tatoeba

Russell was a brilliant philosopher, but even the simplest practical task was quite beyond him.

Source: Tatoeba