Hello,
b/ the problem is caused by this custom CSS code – https://prnt.sc/TAGqVcLdyjST , without this code you will get https://prnt.sc/eOA3oU3SqISl , so delete or change the code.
c/ You may change your button’s colors in Theme Settings -> WooCommerce -> Single product -> Add to cart & quantity -> https://prnt.sc/qsx5gMY2WGbA
If you want to change the icon only in this button you may add one of next custom CSS snippets to your Theme Settings -> Theme Custom CSS -> Global CSS
.single-product-builder .single_add_to_cart_button:before {
content: '\e916';
}
or
.single-product-builder .single_add_to_cart_button:before {
content: '\e93d';
}
or
.single-product-builder .single_add_to_cart_button:before {
content: '\e90c';
}
or
.single-product-builder .single_add_to_cart_button:before {
content: '\e90d';
}
All built-in XStore icons you may find on -> https://xstore.8theme.com/xstore-icons/
d/ We selected for you sidebar position options to Off-Canvas -> https://prnt.sc/BcDLjoptPYWd
Regards