Hey Boris,
welcome to the Fairphone users forum!
Sadly, support reply times are really high - they probably just did not get to your case yet. They have promised improvement, and reported back to have slowly improved, but still a big backlog.
As you requested the return within the legally required time, it should not be an issue to return the case (or at least get the money back) with your first support ticket, also see contactsupport
If you’re in a hurry (or don’t trust the assurance that they will get back to you eventually), try writing to the chat bot again during live chat hours (10-12 CET), but don’t mention that you already have a support ticket. That will let you talk to a human.