Page speed improvement for mobile and desktop

We have WP Rocket premium but it hasn't improved the site speed enough.

Speed issues to be fixed.

To include the following;
Issues to fix on GT metrix
1. Leverage browser caching
2. Defer parsing of JavaScript

Opportunitys from PageSpeed insights desktop

1. Eliminate render-blocking resources
2. Avoid an excessive DOM size
3. Avoid chaining critical requests
4. Eliminate render-blocking resources
5. Ensure text remains visible during webfont load
6. Keep request counts low and transfer sizes small
7. Minimize main-thread work

Opportunitys from PageSpeed insights for MOBILE
9. Reduce JavaScript execution time
10. Reduce server response times (TTFB)
11. Reduce the impact of third-party code Third-party code blocked the main thread
12. Remove unused CSS
13. Serve images in next-gen formats
PINGDOM Opportunities
GRADE SUGGESTION
1. Compress components with gzip
2. Add Expires headers
3. Avoid URL redirects
4. Reduce DNS lookups
5. Use cookie-free domains
6. Make fewer HTTP requests