Merging changes from a copy of a report to the master file

Hi,

I have a master report for onboarding candidates which had some columns that needed updating. I had shared copies of the file with different Function heads by filtering the different functions.

The heads have now updated some columns and sent the files back.

How do I merge only the changes made by the function heads back to the master sheet without replacing the already existing values in other columns? 

Are lookups still the best option or is there a better and faster way to do it?