The Armenian joined the Gunners in January in a straight swap for Alexis Sanchez.
"Of course sometimes you need some refreshing," he told ESPN Brasil.
"And I think this was the best moment for me, because there were a few things that didn't work out in Manchester.
“Because I was 29 years old, I wanted to play more, because I know that in a few years time I'll be able to end my football career, and it's very important for me to make my name bigger.
"That's why, maybe, it was the best moment, and the best time to change something and to get a new challenge, a new club, and start everything from zero.
"I've learned a lot from my previous two managers, Klopp and Mourinho, and I want to learn more from Arsene Wenger as well.
“And it's too early to compare them to each other, I still need time to work with Arsene Wenger. Of course from the time being here I've learned a lot already, and I want to learn more."