My Nephew Is 7 Years Old And Has Some Signs

my nephew is 7 years old and has some signs of autism and not able to speak much. He has even gone through speak and behavioral therapy. But still has difficulty is talking. He can speak small words or 2-3 words sentence. What can be done to increase and improve his speech ?
He has also learned operating computer and play few games without any assistance , could please even suggest activates which could be done to help his gain of knowledge ? As he has learned A-Z alphabets, Numbers , some nursery rhymes.

Thanks a lot in advance for your guidance.