Hi biss-glass.eu,
Thank you for contacting us.
You should be able to translate product variations from WooCommerce > WooCommerce Multilingual > Attributes tab and after that, you need to press the Synchronize attributes and update product variations button, please make sure to take a backup of your site first for security reasons.
Here is a doc for more details:
https://wpml.org/documentation/related-projects/woocommerce-multilingual/#variations
If still an issue persists, I kindly ask that you please provide me temporary wp-admin info (wp-admin URL, username, password) to the Private Content area, this will allow me to thoroughly investigate and address your concerns more efficiently.
Regards,