He said: "For me, Carra is one of the best defenders in the world. He is a very important player for us.
"He was very good again last night, particularly in the second half when they put us under a lot of pressure.
"The only problem is I don't understand a lot of what Carra is saying. It's not so difficult with Sami, but I still need to improve my communication overall with the defenders.
"We have only been together a few months and we've done a lot of work on talking to each other. I'm trying to learn to speak good English as soon as possible so we're still going to improve.
"I'm happy with the three clean sheets in the Premiership, but I always say the most important thing is to win the games.
"If we can keep a clean sheet on Sunday then we will have more possibilities to win the game. It will be tough because Manchester United are a good side and we have a lot of respect for them. But we are doing a lot of defensive work in training and I feel we are working well together."