Hello, Theo,
We’ve checked the translation for the theme and XStore Core plugin and there the texts are changed using Loco Translate.
Sorry, but we do not see why texts on buttons are ‘Voeg toe aan winkelkar’ but not ‘voeg toe aan winkelwagen’. We would recommend you contact support for the Multilanguage plugin.
To confirm that this situation is independent of our theme, you can temporarily activate the default WooCommerce theme – Storefront and check texts then.
The problem can be caused by a 3rd party plugin on your site, server cache, or additional customization in files, please check it by yourself.
Kind Regards,
8theme team