As our shop is still under construction, I sent you the URL via email to your “info@” email-address.
Also, you should easily be able to reproduce the issue by simply installing the “WooCommerce PayPal Checkout Gateway” WP plugin on a clean installation of your “Online-Shop” theme. The button for express-checkout on the product pages will not show up (even with all other plugins disabled), while it will show up, if you switch to some other random WooCommerce theme.
Thx for looking into this!