i new in k2
want to change the style of k2 item and style of categories
i create a categories page and i need to style it as i wish, is there a template do this for just item and categories but still working with another template?
please help me

Start here
getk2.org/documentation/tutorials/item/174-templating-with-k2-and-the-concepts-of-sub-templates

First use the category paramaters to set what you want to show and not to show
Edit category.php for the display of the category view
edit category_item.php for the items display within the category view
edit item.php for the item view
take a look at css4k2 from jiliko.net / k2joom.com for indivual css styling for different categories