A dream featuring a desk represents decisions to be made or the discovery of new things.
If you are sitting down at a desk then it suggests that you are thinking about an aspect of your life or task in detail. It can also symbolize discovery of new ideas.
To be sitting at someone else’s desk suggests that you lack confidence in your abilities in some part of your life.
If the desk is messy then this suggests you need to organize yourself or some aspect of your life better.