How to summarize only selected columns, please check the attached file

[SwathiGanesh]

I have three columns in a table and we are using parameters to select the required column to the table.
Based on the selected column, I need to summarize and do some calculation.
I am stuck and unable to find how to make “VAR SUMMERISE” to work, this variable should summerize the selected columns only. I am using this to find the denominator.
It works fine when all three columns are selected, but I need to summerize based on the selected column
Parameter are [column names]: We have a slicer on the page

🔲Partnername

☑️partnerTYPE

☑️partnercountry

I need a syntax to summarize just the selected columns

Uniques =
VAR sumfc = SUM(salary)
VAR SUMMARISE = SUMMARIZE(Partnername, Partnercountry, partnerTYPE, "Average", sumfc)
RETURN
    IF(
        OR(
            ISINSCOPE('Partnername'),
            OR(ISINSCOPE('Partnercountry'), ISINSCOPE(partnerTYPE))
        ),
        SUM(salary),
        DIVIDE(sumfc, COUNTROWS(SUMMARISE))
    )

[SwathiGanesh]

Can add sample file, please give me permission