Need help with ranking measure

Hi Luukvv93 

To receive below result.

You can modify below DAX expression. 

Rank Top and Bottom Three Sales by Brand =
VAR __grain =
    CALCULATETABLE (
        VALUES ( 'Product'[Brand] ),
        --Rank by Column 
        ALLSELECTED ()
    ) -- replace [Sales] with your Measure
VAR __top =
    RANKX ( __grain, [Sales],, DESC ) <= 3
VAR __bottom =
    RANKX ( __grain, [Sales],, ASC ) <= 3
RETURN
    SWITCH ( TRUE (), __top, [Sales], __bottom, [Sales] )