inflexible position = your mind is set on a particular solution
Meetings are a bit like auctions is explained in the next sentence... "In the to and fro of discussion it's easy to get carried away and make undertakings you later regret." An auction sale is one in which the price for an object is bid higher and higher. If you get caught up in the auction process you might pay too high a price for the object.
knee-jerk reaction = a quick or hasty reaction usually negative
you will be filling in the gaps rather than starting with a blank sheet A blank sheet is a starting point. Filling the gaps means that you already have an outline or idea and all you have to do is to develop or refine the idea.
Student or Learner