To describe which language you speak we use adverbs (по-английски, по-японски) or adverbial phrases (на русском, на японском, на пирахан). There is no way to use the adjective directly with speaking. Говорить only attaches things you speak as objects (not the language you speak them in).
However, in Russian you can say that you "know" the language. Then you can use английский or английский язык as a direct object of the verb.