Germany never tried to change the border with Poland.

1. In 1950 the German Democratic Republic accepted the Oder-Neisse line as border between Germany and Poland in the Treaty of Zgorzelec ("Vertrag von Görlitz" in German)
2. In 1970 the Federal Republic of Germany accepted the Oder-Neise line a border between Germany and Poland in the Treaty of Warsaw
3. In 1990 the unified Germany and Poland signed the German - Polish Border Treaty and Germany accepted the Oder-Neise line as border between the two countries.

Sources:

1 and 2: "Polen und die deutsche Ostpolitik" (Poland and the German Eastern Policy) from Katarzyna Stokłosa - English - Here - Page 536

3: The treaty in German and in an english translation

Germany renounced any territorial claims to the their former east territories to get permission from Four Powers (USA, USRR, United Kingdom and France) for reunification. The Treaty on the Final Settlement with Respect to Germany (known as "Two Plus Four Agreement") was signed on 12 September 1990.