There might be some secrets of the process of learning languages in the difference between literate and illiterate people.
When it comes to learning second language, we Japanese people have been focusing mainly on reading and writing. We don't know how to learn communicating skills without reading or writing.
Therefore, we Japanese can read and write English sentences to some extent. However, we don't speak English well. It is the opposite phenomenon of the natural illiterate people.
In order to improve our speaking skills in English, it might be a good idea to learn language without using letters especially in the initial stage. In addition to reading and writing, we should put priority on conversations also.