In 1970, Reimer graduated from high school from Jürgen Fuhlendorf School in Bad Bramstedt. He got his bachelor degree in agricultural engineering at the Christian-Albrechts-University in Kiel. A year before he became an independent farmer in Hasenmoor.
He was a member of the European Parliament between 1989 and 2019. Since 1989 he was a member of Group of the European People's Party (Christian Democrats), Christlich Demokratische Union Deutschlands (Germany), Committee on Budgets, Delegation to the EU-Chile Joint Parliamentary Committee, and Delegation to the Euro-Latin American Parliamentary Assembly and Committee on Budgets, Delegation to the EU-Chile Joint Parliamentary Committee, The special committee on the policy challenges and budgetary resources for a sustainable European Union after 2013 and Delegation for relations with Australia and New Zealand. He was also a substitute for Committee on International Trade, Committee on Foreign Affairs, Delegation for relations with Japan and the Committee on Foreign Affairs.
He was also a Vice-Chair for Delegation for relations with Australia and New Zealand, Delegation for relations with Sweden and Delegation to the EC-Sweden Joint Parliamentary Committee.