Dealing with Headcount data

[Beginner]

Hi,

I have headcount data in this format.

https://docs.google.com/spreadsheets/d/1QN8k_nvg4-_f8SoaKo_QuB398Z2-kVjv84lxfkuGaKs/edit?usp=sharing

I want to use Looker Studio to aggregate this data so that I can get the number of staff per Group, Office, Business,  and quarter in Scorecards and Tables. How would I ensure that the single month figures are not duplicated?

eg:

For the number of staff at each office, the monthly number of staff would need to be averaged

For the number of staff for all offices the average for each office would have to be totalled.

Would I need to set up this kind of calculation up for every dimension I want to show (eg per quarter, business, group etc)??

Thanks for any suggestions!