Short answers, pulled from the story.
The Battle of Crete began on the morning of the 20th of May 1941 with German airborne landings, and the island came under German control on the 1st of June 1941, making the battle approximately eleven days long. Allied evacuation from the south coast ran from the 28th of May to the 1st of June.
The Allies had detailed intelligence from Enigma decrypts about the German plan, including the date and objectives, but misread the threat. Freyberg concentrated forces along the coast to guard against an amphibious landing rather than defending Maleme Airfield, the principal German target. A communication breakdown between two New Zealand officers on the night of the 20th-the 21st of May left the airfield undefended, allowing German reinforcements to land by air.
Operation Mercury, codenamed Unternehmen Merkur, was the German airborne and amphibious assault to capture the island of Crete in May-June 1941. It was the first large-scale airborne invasion in military history, deploying 10,000 paratroopers, 750 glider-borne troops, 5,000 airlifted mountain soldiers, and 7,000 seaborne troops.
The Royal Navy suffered severe losses from Luftwaffe air attacks during the battle. The cruisers Gloucester and Fiji were both sunk on the 22nd of May 1941, and the destroyers Kelly and Kashmir were sunk on the 23rd of May. By the end of the campaign the Royal Navy's eastern Mediterranean strength had been reduced to only two battleships and three cruisers, with 1,828 naval personnel killed.
Cretan civilians joined the battle armed with whatever they could find, including kitchen knives, farm tools, and old rifles retrieved from local museums. They participated in counter-attacks at Kastelli and Paleochora and harassed German paratroopers across the island. The Abwehr had predicted civilians would welcome the Germans as liberators, a prediction that proved entirely wrong.
The battle effectively ended large-scale German airborne operations. Hitler concluded that paratroopers had lost the advantage of surprise and directed that they be used as ground troops in subsequent operations. General Student later said Crete was the death of the airborne force, and the 7th Fliegerdivision, decimated in the battle, was never rebuilt. The Western Allies, by contrast, were impressed by the potential of airborne assault and expanded their own parachute forces.