Why was fdr willing to make concessions to stalin at yalta when determining the fate of postwar germany? what decisions were made there?

President Franklin D. Roosevelt was willing to make concessions to Joseph Stalin at Yalta conference because he wants the Russians to participate in the Pacific Theater against Japan to lessen the american casualty in the war. Also to make the Russian to join the United Nations. Decisions such as giving the entire eastern bloc to Russian sphere of influence and dividing Germany between the Big Three was also decided in the Yalta Conference.