De Jong arrived at City from Holland in January.
"I'm still learning," he told the club's website. "You will always pick up a couple things during any game, and I'm not going to finish learning just yet.
"A game like West Ham was ideal for this, you have to keep working hard in those sort of games and stay solid in defence so that's when you keep learning about your own game."
De Jong added: "The level of training is really good, and that means that we can produce performances like the one against West Ham because everyone is competing, everyone wants to show themselves and everyone is at the top of their game.
"That's coming out both in training and in games, we're all still learning of each other's qualities and it's making us get even better."