Short answers, pulled from the story.
The German signals unit known as FAK 621 began reading British tactical codes in August 1941. This intelligence stream continued through January 1942 and provided Erwin Rommel with high-quality information about enemy movements.
A single German motorised division required thirty tons of fuel per day during Operation Crusader. The force needed hundreds of lorries to move supplies across the desert while road transport consumed thirty to fifty percent of all fuel deliveries.
The garrison at Tobruk consisted mainly of the 9th Australian Division who defeated an Axis attack in May 1941. They settled into active defense by patrolling most nights and reconnoitering enemy positions.
Before dawn on the 18th of November, the 7th Armored Brigade advanced northwest toward Tobruk while the 22nd Armored Brigade moved west. The 22nd Armored Brigade met the Ariete Division at Bir el Gubi after which twenty-five new Crusader tanks were knocked out for an Italian loss of thirty-four tanks.
On the 7th of December, Rommel decided to narrow his front and shorten lines of communication by abandoning Tobruk. He withdrew to positions at Gazala which had been prepared by Italian rear echelon units and occupied by eight December.