The Liverpool loanee's first goal for the capital club kick-started a third successive victory that leaves them fifth in the German top flight.
Loris Karius was an unused substitute at RheinEnergieStadion.
In the Championship, Harvey Elliott, Harry Wilson and Sheyi Ojo all featured.
Elliott played the full match as Blackburn Rovers drew 1-1 with Luton Town, and Wilson also completed the 90 minutes of Cardiff City's 1-1 draw with Millwall. Ojo, meanwhile, came off the bench at The Den.
Elsewhere, Ben Woodburn appeared as a substitute as Neil Critchley's Blackpool claimed a fifth consecutive win by beating Peterborough United 2-1 in League One, and Kamil Grabara's AGF Aarhus lost 2-1 to the Reds' Champions League opponents FC Midtjylland.