After watching the show on U-869, my interest in U-boats has once again been sparked. I revisited \"Iron Coffins\" by Werner and was paying closer attention to the details during this latest reading. Werner mentions U-557 coming into Kiel for an overhaul which included the engines and batteries, not to mention repairing damage from a recent accident. Werner stated that in barely over a week, U-557 was heading out for her first patrol. While I have never worked on any ship, much less a submarine, I am a diesel mechanic, and have a hard time believing this rapid turnaround. My questions are as follows:

Were overhauls performed in this time?
Perhaps overhaul means something different than my interpretation?
Is \"Iron Coffins\" historically reliable?

Thanks you in advance for your response.

Tom