Formulas and functions

NathanRodrigues 

We could help with VBA though it is becoming less important to the development of Excel solutions.  That said, the solutions I have put forward are all worksheet formulas.  Cell references (e.g. $C$11:$G$41) do not appear because I use Defined Names (see Formula ribbon tab).  The LET function is one of a small number of Excel functions that has an alternating pattern of parameters (in that case a variable name followed by a formula).  I separate the parameter pairs by using Alt/Enter which inserts a new line and gives the function a code-like appearance. 

I suggest you look at the workbook I enclosed and look up the functions used there.  You are correct that the FILTER function could be used.

= SUM(
     FILTER(QtyBuy, Clients="Client Marcos")
  )

but SUMIFS is better when it comes to building the results as an array.  To obtain the results as a dynamic array using FILTER would require

= MAP(UNIQUE(Clients),
     LAMBDA(aClient,
         SUM(FILTER(QtyBuy, Clients=aClient))
     )
  )