Define user agent groups in the W3 Total Cache plugin
User agent group included in the plugin W3 total cache has exceptional advantages, suitable for mobile users. You can see that there are groups and in the general settings there are only 2 (two) groups.
The group is divided into 2, viz High and Low. Where the two groups are cell phone lists. In the upper group there are smartphones and in the lower group ordinary browsers, which are often used by mobile visitors.
The advantage is that you can select the themes you want to use in the mobile version and easily activate them. This method works if you already have a mobile theme and don’t choose a desktop theme as it can get messy later!
Many mobile themes can be found in WordPress, where else if not in search engines. Please search first, then upload and extract for / public_html / wp-content / themes.
After that, let’s start with the following procedure!
Please check the display in the admin panel beforehand to see whether the mobile themes have been entered.
When it pops up just go to the w3 total cache menu and click User agent groups or directly to
http: //domain.url/wp-admin/admin.php? page = w3tc_mobile
Change domain.url to your website url.
Please check the groups above and below and select the mobile designs that were uploaded previously.
Just pick and choose topics, so there is no need to fill in settings like redirect and others. Just click save Changes
If you are a mobile plugin user like mobilepack, mobilepress or wp mobile Detector. Don’t select a theme, just check and leave the theme option checked Run through.
If you don’t know how to use the w3 total cache plugin, you can find out more about search engines, and there will be many explanations, namely storing visitor caches to facilitate access to the website and one of the uses for this can be the user agent group SEO improve on googlebot-mobile. So don’t forget to optimize the themes used (mobile version) 
The process can be understood as well as possible, anyone who would like to ask is welcome to leave a comment.
Hopefully useful and good luck
