We are constantly working on the speed of XStore.
GTMetrix changed its testing system, and all the sites that had A, B scores get C, E or F. If we check your site using Pingdom we get much better results. Google Pagespeed (and now GTmetrix) always scores with 20-50 points mobile performance for 99% of websites built with WordPress.
Please follow this article – https://xstore.helpscoutdocs.com/article/100-how-to-speed-up-my-website
Then provide temporary wp-admin access, so we can take a closer look at your settings.
