Child theme style.css isn’t overwriting parent style.css

Style is not from parent CSS it is from themes/optimizer/style_core.css
Then you can enqueue your child CSS on highest priority.

enqueue the parent style then child style on high priority

function enqueue_parent_theme_style() {
wp_enqueue_style( 'parent-style', get_template_directory_uri().'/style.css' );
}
add_action( 'wp_enqueue_scripts', 'enqueue_parent_theme_style' );
function enqueue_child_theme_style() {
wp_enqueue_style( 'child-style', get_stylesheet_directory_uri().'/style.css' );
}
add_action( 'wp_enqueue_scripts', 'enqueue_child_theme_style', 100 );