hello everyone my son is 2 year 9 month old, when he was 18 month old he say mumma papa bhai fufa baba dadi many words and respond to his name, but now he don't call someone and don't show any response when we call him or say him to do something, but he play with us, smile while playing, please give me some tips to encourage him to speak and how can I teach him to respond to his name.