SUM every 5th column

I have a LO Calc table for a competition. There are 4 columns for the 4 weeks of the first month followed by a 5th column for the monthly best result out of the previous four weeks, followed by another 4 columns for the 4 weeks of the next month and followed by another column for the monthly best result out of the previous four weeks, etc, up to 12 months. What I need is best monthly result out of four previous weeks, and a sum of five best results of all months. I searched a lot and tried many examples but with no satisfying result.
Any help would be appreciated.

Sample file: https://ask.libreoffice.org/upfiles/1536762079406208.ods

Please share a file sample with what you like and how data are in.

Attached is an Example file with description therein.Example.ods