Hello,
1) Make sure that your translation file is up to date https://xstore.helpscoutdocs.com/article/103-translation-files-update and that the mentioned string is translated. If you still have the issue then provide us with WP Dashabord access to check the problem in more detail.
2) a. These buttons are not the XStore theme buttons, they come from the Elementor plugin http://prntscr.com/v0igrq because of option that you enabled in the Elementor settings. And click works ok https://gyazo.com/96a7789dd08cc80162e1cb398328ca08 but it takes some time to load the cart page.
b. Contact Elementor plugin support if they have any option to change it for those buttons. Border radius for buttons of our theme you can change in Theme Options > Styling > edit Light, dark and Active buttons border-radius.
c. Disable Elementor buttons (Elementor > Settings > Integrations > WooCommerce > Mini Cart template > disable)
3) Provide us with WP Dashboard and FTP access to your site to check if we could add compatibility with that plugin.
4) Add the below code to Theme Options
.mobile-header-wrapper .et_b_header-search .input-row {
border: none;
}
5) Don’t see issues with that button https://gyazo.com/537ef41a8707f10998559b25ab1455a9
Regards