Short answers, pulled from the story.
The Siegfried Line campaign was a phase of the Western European theatre of World War II involving engagements near Germany's Siegfried Line defensive fortifications. It spanned from the 15th of September 1944, when Operation Overlord concluded, to the 16th of December 1944, when the German Ardennes counteroffensive, the Battle of the Bulge, began.
A severe logistics crisis halted the Allied advance. Supply lines still ran back to Normandy, major forward ports were either held by German forces or destroyed, and the port of Antwerp, though captured largely intact on the 4th of September 1944, could not be used until the 28th of November because the Scheldt estuary remained in German hands. The Red Ball Express truck operation could not move enough supplies to sustain the rapid advance.
Operation Market Garden, launched on the 17th of September 1944, attempted to seize a Rhine bridgehead at Arnhem to outflank the Siegfried Line. The operation failed when the British 1st Airborne Division suffered approximately 77 percent casualties by the 25th of September. German strength was underestimated, a copy of the Allied battle plan was captured, and bad weather prevented aerial resupply and reinforcement.
The Battle of the Scheldt was a multi-phase operation conducted primarily by the Canadian First Army from September to November 1944 to clear German forces from the Scheldt estuary and open the port of Antwerp. Antwerp was essential to Allied logistics, but remained unusable while the estuary was held. The campaign concluded on the 8th of November after amphibious forces entered Middelburg, and the first supply convoy reached Antwerp on the 28th of November 1944.
The Battle of Hurtgen Forest, launched on the 19th of September 1944, cost the Allies 33,000 casualties from all causes. The battle was expected to last a few weeks but continued until February 1945. Modern historians have argued the outcome was not worth the foreseeable losses and that American tactics favoured the German defenders throughout.
Allied forces crossed the Rhine at four points in early 1945. On the 7th of March, the U.S. First Army captured the Ludendorff Bridge at Remagen after the Germans failed to destroy it. The U.S. Third Army crossed at Oppenheim on the night of the 22nd and the 23rd of March. Montgomery's 21st Army Group crossed at Rees and Wesel on the 23rd and the 24th of March in Operation Plunder. The U.S. Seventh Army crossed between Mannheim and Worms on the 26th of March, with the French First Army adding a crossing at Speyer. An estimated 280,000 German prisoners were taken west of the Rhine before these crossings.