Hello, @Dionizio Find,
1- Simply go to the Dashboard >> XSTORE >> Theme Settings >> WooCommerce >> Single Product Builder >> Prev/Next product navigation >> and disable it from there see the image: https://postimg.cc/jLhFxg8y then check back to your site after clearing the browser cache.
2- In order to solve your issue simply go to the Dashboard >> XStore >> Theme Settings >> Theme Custom CSS >> Global CSS and then paste the below code at the bottom of the CSS box there.
.swiper-vertical-images .vertical-thumbnails-wrapper img{border-radius:10px !important;}
Then save settings and check back to your site after clearing the browser cache.
Regards 8Themes Team.