Short answers, pulled from the story.
The Siegfried Line campaign began in September 1944 when Allied armies advanced faster than their supply lines could support. Units of the U.S. 12th Army Group lacked fuel or ammunition because railways lay largely ruined and major forward ports such as Calais, Boulogne, Dunkirk, and Le Havre stayed in German hands.
It took until the 28th of November 1944 for the first convoy to enter the port of Antwerp after Canadian First Army operations began on the 12th of September 1944. The port stood 90% intact when captured but remained useless without sea access through the Scheldt estuary due to German defensive positions.
Operation Market-Garden failed to secure the Arnhem bridge despite three and a half divisions of American, British, and Polish paratroopers dropping to capture key bridges. By the 25th of September 1944, British paratroops had suffered approximately 77% casualties while the 82nd Airborne Division delayed ground relief forces by 36 hours.
The Battle of Hürtgen Forest cost 33,000 casualties from all causes including wounded, missing, and dead because terrain favored defenders and fighting stretched until February 1945. Modern historians dispute whether outcomes justified foreseeable losses arguing tactics played directly into German hands.
The Battle of the Bulge started on the 16th of December 1944 when Plan Wacht am Rhein targeted the Ardennes region intending to split American and British armies apart. Total losses reached 400,000 men among stubborn German defenders during the campaign that ended with Germans pushed back to starting points by the 25th of January 1945.