Hi @Silke38
Airbnb takes host cancellations very seriously and one of the penalties is blocking out the dates in question in your calendar as you have indicated they aren't available.
Have you looked through the Airbnb Help Centre to give you a better understanding on how Airbnb works and your rights and responsibilities as a host, including the section on host cancellations?
You can call Airbnb and ask if they will unblock them - but in most cases if you cancelled because your calendar wasn't up to date, or you hadn't updated your prices, they will keep the dates blocked.