Go to Plugins and search for the plugin "Autoptimize".
After installing and activating, go to Dashboard -> Settings -> Autoptimize.
Look at the screenshots below to set up the options for "JS, CSS & HTML". Make sure you enable the recommended options (green ticks) to keep loading time rapid.
Autoptimize settings screenshot 2
Autoptimize settings screenshot 3
Autoptimize settings screenshot 4
With Images options:
Autoptimize image options
Remember to choose the 2nd option (lazy option images).
Extra options:
Autoptimize extra options
In the "Google Font" section select the first option "Leave as is".
2
Install WP Super Cache
Plugin Cache is used to manage and clear theme caches.
Install and activate WP Super Cache.
Go to Dashboard -> Settings -> Cache.
Choose the option "Caching on" to enable the plugin.
Tick "Send non-secure (non https) request for homepage", then click "Test Cache" to check it.