TTFB and Caching issues

Hello there I am using cloudflare and having two issues :
One on the ttfb and the other on the woocommerce cart.

When setting up Cloudflare with no settings and page rules, my ttfb is around 1- 2 seconds. When setting up “Cache everything” and Edge TTL in page rules I am getting a nice ttfb of less than 200 ms but my woocommerce cart is mixing up users (including anonymous users) products.

It seems that the issue is coming from dynamic content being cached because when I remove rules the site works properly. I have tried to bypass cache on cart and checkout page but it is still mixing up the cart and not removing products or just showing an empty cart even if the products have been added.

I am using Cloudflare free so I can’t bypass cache cookies. I wanna know if there are any ways to bypass cookies without Cloudflare page rule or if the issue is really coming from there.

I have tried this solution :
https://guides.wp-bullet.com/cloudflare-cache-wordpress-posts-and-pages-guide/
but I cant make it work, my links wont change.

Any ideas on how to solve that?

The page I need help with: [log in to see the link]