Hi Birgit,
I’m sorry to disappoint you but unfortunately Events Calendar and its add-ons are not fully compatible with WPML. Please see this Knowledgebase article which outlines the issues → https://theeventscalendar.com/knowledgebase/can-your-products-be-used-on-multi-lingual-sites/.
Please let me know if you any follow-up questions or if there’s anything we can do to minimize the disappointment here. I’m sorry about the incompatibility, but please know that we’re working hard on some code fixes over the next view releases of the plugins to improve compatibility.
Thank you,
George