Ostermann was born on 30 April 1958 in
Detmold,
North Rhine-Westphalia. After passing his A levels (
Abitur) in the town of his birth and completing his
basic conscription, Ostermann passed his studies in
law in
Passau and
Göttingen. Ostermann was employed from 1990 to 2001 as an administrative lawyer (
Verwaltungsjurist) in the district of
Güstrow in
Mecklenburg-Vorpommern and from 1994 also as deputy
Landrat. In 2002 he became the First District Councillor (
Erster Kreisrat) and General Representative (
Allgemeiner Vertreter) of the district council for
Soltau-Fallingbostel district (now
Heidekreis district). After the death of the
Landrat, Hermann Söder, in 2006, Ostermann took over the post, initially in an acting capacity, and subsequently ran for the office, supported by the newly formed alliance of
Kompetenz für SFA, that was composed of representatives of the
SPD,
Alliance 90/The Greens, the Citizens' Union (
Bürgerunion) and the Walsrode Citizens List (
Walsroder Bürgerliste). In the elections on 14 January 2007 he won through with 52.8 % of the vote against his rivals,
Karl-Ludwig von Danwitz (
CDU) and Knut Maass (
FDP). == Private life ==