Pivot Table : How to group by month if the dates are column headers?

Current table:

          5/4/2020  5/11/2020   5/18/2020   5/25/2020   6/1/2020Jim          2         5            6          7           6Jane         3         2            4          3           3Adam         1         4            2          8           4

Desired table:

         May    JuneJim       20    6Jane      12    3Adam      15    4

Google sheet with problem: https://docs.google.com/spreadsheets/d/1gPSjdrF9ngaJj0KDa82qPN3iwf9Qch3jIBH0fXx7Xxo/edit#gid=1324843131