Formula

Hi Augustas-ase 

So let me assume "Category" is the only column on your table visual and "Sales" is the factuals.

DAX formula below:

% Sales = 
var _sumOfSales = Sum(Table'Sales')

var _percent = Calculate(_sumOfSales,ALL(Table'Category))

return

_sumOfSales/_percent

(put your columns accordingly and change the data presentation to %)

Please do hit like if this provides you with a solution

Regards

darkinvader