Excel: counting data for different days of different weeks ( variable rows count )

I have a report with data for different dates. As I have a daily report, I need to sum the quantity of data ( Paid, Done ) column for an every specific week. With the help of Weeknum I detected the number of a week, and now I need to calculate the sum of this data for a specific week. How can I accomplish that? I tried SUMIF - it didn't help.