Joomla Global Settings

1) Gzip Compression

Go to Top Menu, select Site > Global Configuration > Server tab, and switch the Gzip Page Compression to YES option

2) Minimize/Compress  JavaScript/CSS/HTML

Use a plugin like  JCH Optimize

Take care, because you must use the proper level of optimization for your site

You can check the results using Gtmetrix

3) Using CDN

(minimizing the distance between your visitor and your CMS server using the CDN network)

4) Use page speed optimized extensions

  like: 

 JavaScript Async and Defer 

 jQuery Easy

 and more