Magento is a very slow e-commerce system and initially the pagespeed score is very low. To increase pagespeed, you need to take some steps, which I will describe. The post will be updated.
Install the nginx / apache pagespeed module
This is a special module from Google that will do all the dirty work for you. Imagine that a content manager has uploaded a 15 megabyte image to the site, naturally it will take a long time to load and visitors may leave the site. This module will compress the image on the fly depending on the visitor’s device (mobile, tablet, desktop) and give him an optimized small image.
The pagespeed module automatically converts non-optimal graphic formats (gif, jpeg) to webp, which significantly increases the score.
Also, the pagespeed module can combine different css and js, because each separate http request increases the page load time. If all resources are combined, the page will load faster.
The pagespeed module can detect if gzip compression is enabled and enable it automatically if you haven’t enabled it yourself.