Hello @Andrea8402
If you go click on the Community Center here (top right hand side) you'll see Help Center and you can make a search on how to synchronise calendars with multiple listings. The help link you need is the one showing below:
https://www.airbnb.com/help/article/1864
As for charging extra for parking, I think you should make this very clear on your listing that there will be an XX amount to pay if someone wants to use your parking. It is something that is highly sought after but haven't heard anyone charging for this facility.
You should make sure in the message stream with guests that they agree to this extra cost and then once they have confirmed their reservation you can use the "Request money" via their reservation number if you want it to go via Airbnb.