Karius has joined the Germans on a season-long loan.
He told BILD: “I wasn't sure whether to go or stay.
“The option to stay was definitely there because, even if you are not the first goalkeeper, you get your playing time through the cup competitions and the many games.
“Then the decision matured that I wanted to be in goal week after week.
“I still have a few more years of contract with Liverpool, and I don't know what the situation will look like next summer."