Peter and Sam had lived in London for five years, by the time they ___ Munich. I can't think of any form of 'be' that fits the second gap. You could say something like 'by the time they went to Munich' or similar. Do you have an example?

Peter and Sam had lived in London for 5years, but the time they were to move to Munich.

Is difficult understand it. Do you have to put one word only in each space ? In the first space is "lived", in the second space I don´t know...I ´m sorry