Remove 'Category' prefix

add_filter( 'get_the_archive_title', 'my_theme_archive_title' );
/**
 * Remove archive labels.
 *
 * @param  string $title Current archive title to be displayed.
 * @return string        Modified archive title to be displayed.
 */
function my_theme_archive_title( $title ) {
    if ( is_category() ) {
        $title = single_cat_title( '', false );
    } elseif ( is_tag() ) {
        $title = single_tag_title( '', false );
    } elseif ( is_author() ) {
        $title = '<span class="vcard">' . get_the_author() . '</span>';
    } elseif ( is_post_type_archive() ) {
        $title = post_type_archive_title( '', false );
    } elseif ( is_tax() ) {
        $title = single_term_title( '', false );
    }

    return $title;
}