exclude category from grid

https://codex.www.ads-software.com/Plugin_API/Action_Reference/pre_get_posts#Exclude_categories_on_your_main_page

to exclude only one category, used this adapted code:

function exclude_category( $query ) {
    if ( $query->is_home() && $query->is_main_query() ) {
        $query->set( 'cat', '-1' );
    }
}
add_action( 'pre_get_posts', 'exclude_category' );

code goes into functions.php of the child theme.

you will need to know the category ID of the category

worked! Thanks