Website Speed Issue

We are using Wordpress CMS for our website ( blog. Currently our YSlow score is (74%). Due to external resources we are facing issue with website speed. I used many plugins (Far Future Expiry Header, Async JavaScript, HTTP/2 Push etc) to optimized and increase website speed. Please help us to know how to solve below asked issues on WordPress website.

  1. Add Expires headers
  2. Make fewer HTTP requests
  3. Reduce DNS lookups
  4. Use cookie-free domains

Please check the given URL and attached image for better understand.