Totals monthly

Formula on b2 to drag right and downwards,
totals for seller 1 from raw data sheet2

Yes that is it , I have data huge ,
equivalent to more than 5000 row ,
this will be zoom done

Or another approach, in B2, copy across and down.

=SUMPRODUCT(--(TEXT(Sheet2!$D$2:$D$12,"mmm")=B$1),--(Sheet2!$B$2:$B$12=REPLACE($A2,7,0," ")),Sheet2!$G$2:$G$12)