How to do it as a Beginner?
Things to learn:
.....so what do you use for running averages for 3/6 months?
P.S.: My answer is going to be different than the solution
Great Challenge and shows the power of the grouping options of the sample and multi row formula tools.
On the downside, the example and output data don't make any sense to me.
As for a 3 month average for 2 month - this is not defined, so I left them blank.
(The average of the first 2 month could be an alternative)