Borussia Dortmund slipped back to the bottom of the Bundesliga despite picking up a point in their goalless draw at Bayer Leverkusen.
Cologne dumped Hamburg right into the thick of a relegation battle with a 2-0 win at the Volksparkstadion.
Ivica Olic has rejoined Hamburg after five years away from the Bundesliga club.
Hamburg's Pierre-Michel Lasogga has hit back at accusations he is overweight by saying he just has a "bigger build".
Schalke went two consecutive home games without a win to end 2014 on a sorry note with a goalless draw at home to Hamburg.
Bayern Munich continued their unbeaten start to the Bundesliga season with a 2-0 win over Freiburg on Tuesday night.
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