Hello,
About “File:theme-functions.php:1509 test” – we’ll fix this issue in the next theme update, or you can just https://prnt.sc/1tt9cs5 – delete this line of code
About “Add to cart”, try to disable all the third-party plugins (including cache plugins), that do not come bundled with XStore https://xstore.helpscoutdocs.com/article/36-included-plugins , clear cache of browser, and check then. Maybe one of the additional plugins is a reason for the problem.
Regards