Luiz struck with a header as Arsenal came from behind to win 2-1.
He said, "It was hard work, I think that's normal. We're playing in Europe, they have a great team with great players. They started the game very well so I was happy because, especially in the second half, we did much better to understand the game. We had the opportunity to play our philosophy and in the end the hard work paid off and we won the game.
"We changed it during the game, it was not just a back four. We tried to create a three of a four depending on the game, depending on how they defended us, depending on our plan for the game. The most important thing is to try and do the job in the best way. I think we did that in the second half."
On playing in front of fans again, Luiz added: "It's a great feeling, even against us, it's a great feeling. If you think about football, our job is to play for the fans, for everybody, to make people happy so to have this feeling again is always great."