CSS loaded two times in child theme….

Hello,

I would like to ask you for a help.
I have child theme (of Genesis), I have tried a lot of functions, but nothing works as I expected.

1) Child CSS is loaded two times:

add_action( 'wp_enqueue_scripts', 'my_enqueue_styles' );

function my_enqueue_styles() {

    /* If using a child theme, auto-load the parent theme style. */
    if ( is_child_theme() ) {
        wp_enqueue_style( 'parent-style', trailingslashit( get_template_directory_uri() ) . 'style.css' );
    }

    /* Always load active theme's style.css. */
    wp_enqueue_style( 'style', get_stylesheet_uri() );
}

2) Child CSS is loaded one times, but I have to use !important everywhere

add_action( 'wp_enqueue_scripts', 'theme_enqueue_styles' );
function theme_enqueue_styles() {
wp_enqueue_style( 'twentyfifteen-css', get_template_directory_uri() . '/style.css' );
}

Is there an code, to load original css and override it by main css, without necessity to use !important or to have it loaded two times?

Thanks you ver ymuch