Sort post in a category by title, not by date

https://codex.www.ads-software.com/Function_Reference/query_posts

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

try to add this to functions.php of your theme:

function sort_category_archives( $query ) {
    if ( $query->is_category() && $query->is_main_query() ) {
        $query->set( 'orderby', 'title' );
        $query->set( 'order', 'ASC' );
    }
}
add_action( 'pre_get_posts', 'sort_category_archives' );