7,800 not bad for an Asian.
Practice makes perfect, especially reading books in the areas that interest you.
If you can find translations of Orthodox Christian books into Japanese and English. First read the book in Japanese to get a basic idea, and then read it in English. Translations are not word for word, but in reading the English translation, you will learn a lot of new words.
I got the Chronicles of Narnia
which are translated into many languages.