Short answers, pulled from the story.
Allied-occupied Germany began with the Berlin Declaration on the 5th of June 1945 and formally ended with the establishment of West Germany on the 23rd of May 1949. In the west, the occupation formally concluded on the 5th of May 1955 when the Deutschlandvertrag entered into force, while full sovereignty for a reunified Germany was not achieved until the 15th of March 1991.
Germany was occupied by the United States, the United Kingdom, the Soviet Union, and France. Each power administered one of the four occupation zones established by the Potsdam Agreement of the 2nd of August 1945, with Berlin separately divided into four sectors among the same powers.
The Morgenthau Plan was a proposal by Henry Morgenthau Jr., Roosevelt's Secretary of the Treasury, to break Germany into four autonomous states and strip it of its industry, reducing it to a chiefly agrarian economy. The plan was opposed by Secretary of State Cordell Hull and War Secretary Henry L. Stimson, and Roosevelt distanced himself from it after major American newspapers reported on the idea.
The Potsdam Agreement assigned all German territories east of the Oder-Neisse line to Poland and the Soviet Union, covering eastern Pomerania, Neumark, Posen-West Prussia, East Prussia, and most of Silesia. Most German citizens in those areas were subsequently expelled, and the September 1990 Peace Treaty eventually confirmed the northern portion of East Prussia as the Kaliningrad Oblast within the Russian Federation.
Food conditions were severe across all zones. By the spring of 1946, the official ration in the American zone was no more than 1,275 calories per day, with some areas receiving as little as 700 calories. In the British zone, publisher Victor Gollancz documented in late 1946 that Dusseldorf residents were receiving approximately 770 calories per day against an official allocation of 1,548.
The Soviet Union withdrew from the Allied Control Council on the 20th of March 1948, effectively ending joint Allied governance of Germany. This breakdown led to the Berlin Blockade from June 1948 to May 1949, and ultimately to the creation of two separate German states: the Federal Republic of Germany on the 23rd of May 1949 and the German Democratic Republic on the 7th of October 1949.