Thank you both for the answers.
- Felix: When using Smart search filter web part: what values do you use in the values fields?
SKUName ASC;;name: A to Z
SKUName DESC;;name: Z to A
2.Jan: I want the user (when in the page)to have multiple sorting options that he can define on the search results.
I want the user to have the option to apply different sorting possibilities when he already has the results not when he arrives to the page.