Good afternoon Jukka and welcome back!
Thank you for reaching out to us.
We are sorry to hear about the translations not being accurate on your site.
I would love to help you with this topic.
As a first troubleshooting step, could you please provide us with your complete system information in a private reply using the instructions found in the following link?
https://theeventscalendar.com/knowledgebase/sharing-sys-info/
Secondly, sometimes, there are indeed issues with the translations packaged with plugin updates (po files). When that is the case, you can always head over here to find the most updated and complete files: http://translations.theeventscalendar.com/projects
You can then simply overwrite the ones found in the /lang/ folder of our plugins or better yet put them in /wp-content/languages/plugins/ so that they do not get updated when you upgrade the plugin.
Let me know how that goes.
Best regards,
Geoff B.