Hello,
Is it possible to remove "special items" functions on front end editor for one user categories but not for administrator?

Thanks for help
Regards

K2 does not have special items. It has featured items.
If that is the case, then you can override the itemform.php file which the front-end submission form.

More info on overrides can be found here: getk2.org/documentation/tutorials/174-templating-with-k2-and-the-concepts-of-sub-templates