Good evening Olaf and welcome to the Events Calendar forum!
Thank you for reaching out to us.
We are sorry to hear about the issues you are experiencing while trying to create WooCommerce tickets.
I would love to help you with this topic.
As a side note, it is currently not possible to change ticket types after they have been initially created.
Furthermore, I believe you might have accidentally posted this in the incorrect forum (pre-sales).
Provided you have a valid Event Tickets Plus license, you would benefit from better support by going to: https://theeventscalendar.com/support/post/ and selecting Event Tickets Plus from the list (after you login).
With that in mind, 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/
Best regards,
Geoff B.