The midfielder joined the Spanish giants from Bayern in the summer after the Blancos won the Champions League, demolishing the Bundesliga side 5-0 on aggregate.
Kroos has already won the Uefa Supercup and the Club World Cup in his first season with Carlo Ancelotti's men and is targeting more success this term, but admits he has not made a massive step up in moving from Bavaria to the Spanish capital.
"Playing with stars like Cristiano Ronaldo has been brilliant," he told the DFB website. "But at Bayern I also shared a dressing room with world class players.
"As for the sporting level there is not much difference between the clubs. Both are top teams. So far I'm having a great time. The first half of the season was good, but I hope we have a very successful season finale.
"I feel very comfortable here. Of course I had to adapt to some things. The mentality and way of life here are very different than in Germany, but I get along very well with everyone and I am very happy.
"I am very pleased with the signing."
