Hi... first thing you should have to keep mobile away from him and also stop using mobile in front of him. Try to tell him my mobile got broken like that...
Second thing you should have to spend some time with him. And tell him like whenever you want water don't show your pam ask me "wawa" like that. Tell him like Everything u should have to ask with ur mouth don't show me signs. You guys also act like you won't understand stand his signs until he speak himself a little little words. Everyday Try to learn some new words to him. U juz follow these things definitely he will improve himself.