Cookie free domains

Hello everyone,
I’m trying to set up the cookie free domains recommended by GTMetrix. I created for it a subdomain of the type https://static.mysite.com which points to the wp-content of my site.
I also changed the urls in the database, but the appearance of my site is completely broken, as if the style sheets were not loaded. What should I do.
Here is my config in wp-config
:
define(“WP_CONTENT_URL”, “https://static.mywebsite.fr”);
define(“COOKIE_DOMAIN”, “www.website.fr”);
I also use W3 Total Cache and cloudflare as CDN.