Dynamic TopN with RankX

It is unclear on what you mean with "make it work different".

Are you trying to show the 4 items with the highest total sales over a year? or just during the month?

EDIT: 

If took your example file and created the following measure:

SubTotal = CALCULATE(SUM(Base[Valor Total]);ALLEXCEPT(Base;Base[marca]))

I then changed your TopN Measure to:

TopN_total_sales = 
VAR SelectedTop = SELECTEDVALUE('TopN'[TopN])
var RankMarca = RANKX(ALL(Base[marca]);[SubTotal])

RETURN
IF(RANKX(ALL(Base[marca]);[SubTotal])<=SelectedTop;[total_sales];BLANK())

I'll get this as a result:

Result

I hope that this solves your problem!

Kind Regards.

PS: If it does solve your problem please mark this as answer.