Ekkies have the ability to learn a massive vocabulary, however they do need to be comfortable enough to concentrate in their environment (they are masters of 'freeze' factor when they are uncomfortable they little shut down and block things out). I find that once Ekkies settle in and feel confident they start to open up quite a lot.
But let me ask you, why is it important he speaks english?
Maybe just learn his communication- start there. I personally enjoy the way Dimitri communicates with his eyes, talons and feathers. It warms my heart when he is intrigued by new objects, or when he gets excited over favorite foods. I know he is comunicating in his own way: 'oh wow, thank you'.
My green goblin started early speaking, now he talks more than my African Grey. We need to be careful what we say, and many days (when it is sunny outside) we cant even hear the TV over his chatter (sounds cute, but honestly). Currently he says: Hello, Kalimera, Ya Sous, Num nums, Mmmm, Thank you, Big boy, What are you doing, Good morning, Oopsie (everytime he/I drop something), Oh wow, Up, luv you and the 'kiss' sound.... HOWEVER unfortunately: MY LAUGH (non stop), barks like a dog, copies the call of my finch, woodie the woodpecker song (thanks hubby, ugh), sirens from fire trucks/cop cars, the whistle from my kettle, and 'Remy shut up' (what I say when my dog is barking).
We did not 'teach' these words over the last couple months, he just picked them up because we maintain continuity when interacting with him. I never ask him to do them on command- instead we have mutual communication that I enjoy. He does training (like target training, recall) for rewards to strengthen our relationship, and recently he started to throw in words because of the positive reinforcement.
Then there is also a few hours of indistinguishable chatter to him self, which im sure if we are not careful he will pick more up.
Just keep speaking to your bird with enthusiasm, spend as much time as possible with them and ensure they are healthy. I will stress 'healthy' because a healthy bird is a happy bird; be certain that you are not relying on pellets and seeds as a diet. Well balanced fresh food diet and proper enrichment will increase their desire for mutual social interaction.