Kai Havertz's second-half winner earned Bayer Leverkusen their first Bundesliga points of the season as they beat Mainz 1-0.
Bayern Munich made it three wins from three under Niko Kovac in the Bundesliga with a 3-1 victory over Bayer Leverkusen.
Leon Goretzka scored his first goal for Bayern Munich as the defending Bundesliga champions won 3-0 at Stuttgart.
Schalke opened their Bundesliga campaign with a dramatic defeat as they were beaten 2-1 at Wolfsburg on Saturday.
Leon Bailey has signed a new five-year deal at Bayer Leverkusen.
Arsenal goalkeeper Petr Cech has questioned the values of Bayer Leverkusen after the German club mocked his performance against Man City.
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