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According to a Google post on their webmasters blog the mobile-first indexing is more about how they gather content and not necessarily about how content is ranked. I ran your website through Google's Mobile-Friendly Test and everything looks fine. You can check it out here for you: https://search.google.com/test/mobile-friendly. However, when I ran the mobile test I noticed you are blocking a few content resources within the robots.txt file. I'd update that so Google can access the /wp-content/ folder and properly index images within that folder. Back to the mobile issue, personally I don't believe those two issues will be too impactful unless it is impacting the overall user experience. I hope that helps some.