Hello,
1) Do you use a built-in single product layout or created using a single product builder?
2) Use theme and XStore translation files to translate that https://xstore.helpscoutdocs.com/article/30-base-theme-translation
3) Do you want to add that button on the single product? Do you want to add link to the contacts page or get the popup while using clicking the button? Could you, please, provide us with WP Dashboard access to check the single product layout that you use and help you?
Regards