hi iamhttp

Welcome to Excel Fox

What exactly does sumifs do in when checking an array of conditions? does it sum up everything by condition A, and then everything by condition B?(given A and B are in the same column)
SUMIFS as you understand does a conditional sum on the sum range based on the criteria you passed for each criteria range. The thing with passing an array of values in the criteria is that in such cases one will have to sum up the individual array results, which is why you've read else that you need to add a SUM before the SUMIFS. The SUM acts as an aggregation for the individual results of the SUMIFS function

2)why doesn't my code work properly?
Your equation SUMIFS(Quantity,Item,item_list,Sold_Bought,D3,mont h,B1,Char,INDIRECT(B2)) needs the extra aggregation using SUM function

3)how could i have figured this out alone without bothering you guys?
You probably would benefit by some bit of reading. But it's always better to follow forums where experienced Excel experts share their knowledge on the subject, and especially on formulas (both array and non-array). And I'm sure the good ones out there wouldn't mind you 'bothering' them.