Original: Due to a change in Bonn's foreign policy deviced by Scheel together with Chancellor Willy Brandt, the Federal Republic of Germany gave up claims on former territories ceded to Poland, Czechoslowakia and the USSR in 1945 and officially recognized the existence of the GDR.
Simplified: With Willy Brandt his foreign policy meant the Federal Republic of Germany promised not to try and get back the parts of Germany given to Poland and the USSR.