Hey Marlies,
Thanks for reaching out to us!
Unfortunately the stylesheet issue is a known bug in the latest version of the plugin. I’ve added this thread to our internal ticket for tracking this and you’ll be notified as we make progress on this one.
If you have any questions concerning that process, please don’t hesitate to reach out.
For the translation issue, is your WordPress install set to be in Dutch? It looks like we do have the majority of the Dutch version translated as noted here https://translate.wordpress.org/projects/wp-plugins/the-events-calendar so there could be something else going on here if the install is set to the appropriate language.
Thanks!