Hello @Jakub123
A lot of hosts are having issues on this subject with the new version and the only way it seems to modify a minimum stay period for specific dates is to opt in for "professional tools" which is now available to all listings and for all hosts not just those that have 6 listings or more.
This very useful feature gives you a second calendar that Airbnb call "multi calendar" and from this calendar (linear in appearance) you can create "rule sets". Here is one link that explains this but search on Airbnb and you will find a full explanation of what the pro tools have to offer:
https://www.airbnb.com/help/article/2062
Good luck
Joëlle