Google has announced back in July 2018 that Speed is a landing page factor for Google Search and Ads . This announcement is mainly related to mobile searches:
Users want to find answers to their questions quickly and data shows that people really care about how quickly their pages load. The Search team announced speed would be a ranking signal for desktop searches in 2010 and as of this month (July 2018), page speed will be a ranking factor for mobile searches too.Google Post
We are listing here some tools that will help you to optimize your sites for both desktop and mobile use. They are listed in no particular order. We suggest using all of them.
You might want to consider using a CDN and a cache plugin for your site. For WordPress there a lot of good CDN/cache plugins.