Bernardo Silva gave City the lead midway through the first-half before Dino Mavropanos struck with a header minutes later.
Hermansen later told West Ham's website: “It was a tough game, mentally and physically, a tough game.
“A lot of metres running after the ball. Man City are just amazing at keeping the ball, finding the spaces that we leave. A lot of amazing work from the guys.
“We also spoke about it at half-time. Yes, they had a lot of possession, but they didn’t really break us, so it was important that we kept closing down those spaces, and I think we did.
“Of course, they have individual qualities. They break through in some moments on the wings, but we defended so well. It was lovely to be a part of.
“I think it goes well with what I said about them being amazing at keeping the ball. It's tough to chase, especially if you're down.
“I think Man City are so good at using their lead. It was so important that we got this goal from Dinos.
“I have to deal with every situation as it is. I was happy with my handling and the one shot from Rayan Cherki (that I tipped onto the crossbar). I had some good saves on the way as well.
“I think what we have improved the most is our ability to play as a team. and our ability to be on the same page in everything we do.
“Of course, we work hard, everybody does, to improve. But one thing is working in the right direction as well. I think, especially on that point, we've been moving really, really strongly together.
“Also, we deal with our individual situations during the game much better. I just think we've improved so much in that way.”