1. i don’t want to use more plugins in the websites. i just want to use generatepress features to achieve this if possible
No, it’s not possible unfortuanly. You will need to use a plugin or write your own custom functions.
2. What does the default pages for this? i told you that my all contents are done by individual page, and i dont want to install woo plugins,
David was asking if you are using the default pages or custom post types for your content. So you are using pages?
If that’s the case, you can try this snippet to enable categories for pages, please be noted, GP doesn’t control these settings, they are core WordPress settings.
add_action( 'init', function(){
register_taxonomy_for_object_type('category', 'page');
});