YES ... But the problem is that I have no idea how to put single extrafield in 1 items ...

I though already about this, but there is no way (it seems to me) to put them as You suggest becouse by the way, if I have different extrafield in 1 group, then I will see ALL of them, when I assign an ExtraFieldGroup to 1 category and the article include in that category will shows ALL the ExtraField in that group ...

Is like a dog trying to bite his own queue (sorry for my english!) :oD

:o( 

ok, you have to create a new extra field group. there you create your single extra field. then you asign the group to the category and make the extra field available to the item. i think there is only this way to work with extra fields.