=IF(C2=$G$1,IF(A2=F2,B2,0),0)


any cell referred to in this formula is on the sheet where the formula
is placed.

if you want to refer to cells on other sheets you need to tell the
formula which sheet you are referring to;

example;

=IF(Sheet1!C2=sheet1!$G$1, IF(Sheet2!A2=Sheet2!F2,Sheet1!B2,0),0)

You will need to work out which cells are on which sheet and change
the sheet names accordingly. Remember to use ! after the sheet name.