Welcome to the Forum @Robin6 and thank you for reaching out.
When you set a task to repeat, it only appears in Calendar, Timeline and Workload for the next time that is due and not every single time the task is due in the future. Once you mark a recurring task completed, it will generate itself for the next time the recurring task is set to be due. You can learn more about it in the following Guide article: https://asana.com/guide/help/tasks/fields#gl-recurring-tasks
There is a thread in the #productfeedback category regarding this topic: Recurring tasks in calendar view. If you haven’t yet, I would suggest you to upvote it.
I would also recommend you to have a look at Kaitie’s workaround. You might find it useful.
Please let me know if you have any follow-up question!