Suggest Treatment For Speech Delay In A Child

Hello...I have a 30 months old boy who seems to have difficulty understanding instructions. I am very confused. He has speech delay and is receiving therapy. He knows his colors, numbers to 20 back and forth, knows all his letters, even in random order. He had an evaluation done and it stated that he was not autistic. But I am still worried at the fact that when I tell him to do certain things he is unable to do...like if he doesn t understand. How can I help him?