For an hour, the two teams appeared to be locked in a tight battle that could be decided by one goal.
But once the Reds did score, the floodgates opened and they won comfortably thanks to a Luis Diaz hat-trick.
"I think we did really good in the second half," Gravenberch stated post-game.
"In the first half (it) was a bit difficult. Leverkusen did it good, they pressed us really good, but I think in the second half we played with more intensity, pressed them really good and after we scored four, so we're really happy tonight."
On the step up in intensity, he added: "I think that is the key and also in the second half Anfield was amazing. Then you also get more power to show yourself and you see in the second half we scored four.
"(The atmosphere was good) also against Brighton on the weekend. It was amazing and today as well. They really give us power when they're like this."