VBA to sum values ​​based on the values ​​in column

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hi.
I've got some problem. I need a macro (I cant, use pivot table)which will sum up values from column F based on value from column B and resluts should be shown in column G. I hope that picture or file will be helpfull to understand my problem
I can add that values in column A are unique, but in column B they not. Furthermore my table usually got something between 500 and 900 rows.
I have no idea how to write this in vba or any other idea to do this. I'm a begginer in vba so I really count on Your help.
Thanks in advance.