A little background on the false guesses
Frank-Walter Steinmeier: current president, chancellor candidate in 2009
Franz-Josef Strauß: chancellor candidate in 1980
Friedrich Ebert: president from 1919 to 1925
Harald Schmidt: comedian
Heinrich Brüning: chancellor from 1930 to 1932
Martin Schulz: chancellor candidate in 2017
Angelo Merte: Parody of Angela Merkel from a somewhat infamous sketch
Armin Laschet: chancellor candidate in 2021
Cem Özdemir: minister from 2021 to 2025
Erich Honecker: leader of East Germany from 1976 to 1989
Gustav Heinemann: president from 1969 to 1974
Herbert Köhler: parody of former president Horst Köhler from yet another sketch
Otto von Bismarck: chancellor from 1871 to 1890
Paul Ehrlich: scientist
Richard von Weizsäcker: president from 1984 to 1994
Sebastian Kurz: chancellor of Austria from 2017 to 2019 and from 2020 to 2021
Ursula von der Leyen: current president of the European Commission, former minister under chancellor Merkel
A little background on the false guesses
Frank-Walter Steinmeier: current president, chancellor candidate in 2009
Franz-Josef Strauß: chancellor candidate in 1980
Friedrich Ebert: president from 1919 to 1925
Harald Schmidt: comedian
Heinrich Brüning: chancellor from 1930 to 1932
Martin Schulz: chancellor candidate in 2017
Angelo Merte: Parody of Angela Merkel from a somewhat infamous sketch
Armin Laschet: chancellor candidate in 2021
Cem Özdemir: minister from 2021 to 2025
Erich Honecker: leader of East Germany from 1976 to 1989
Gustav Heinemann: president from 1969 to 1974
Herbert Köhler: parody of former president Horst Köhler from yet another sketch
Otto von Bismarck: chancellor from 1871 to 1890
Paul Ehrlich: scientist
Richard von Weizsäcker: president from 1984 to 1994
Sebastian Kurz: chancellor of Austria from 2017 to 2019 and from 2020 to 2021
Ursula von der Leyen: current president of the European Commission, former minister under chancellor Merkel