Merging columns and add new fields

Hi, 

I have the following dataset:

...and i am trying to merge columns (from Initial Interest Conversion Time) untill PO this Quarter Conversion Time), so then i have the average of each of those columns, per stage, per day..

the end result should look like this more or less:

(i dont need to have all the dates in the calendar; only the dates in the Opportunity Created Date column in the illustration above)

the idea of doing this is to, when building a clustered bar chat, i can have the stages as a Legend with ther respective values.
So if someone have a better idea on how to get this illustration without doing a workaround with the data, it is also valid.

Thank you very very much!