Things would be much simpler if you just sorted columns A and B on column B descending.
If that is not possible, then enter the formula
=LARGE(B$1:B$3,ROW()-ROW(A$1)+1)
in cell D1 and enter the formula
=XLOOKUP(D1,B$1:B$3,A$1:A$3,"?",0,1)
in cell C1. Change each $3 (three of them) to match the last row of data in your worksheet. Copy these two cells to all the cells down to the last row of data.
You will have to deal with the case when two salers have the same sales.