Hello @Michal19,
I'm a little bit confused. You say the host declined the request but later call it a cancellation.
Did the host first accept the request and later cancel the booking? If so then yes, you've been charged the €150.
If you sent a reservation request but the host responded with "Decline" then you haven't been charged the €150.
If you were charged the €150 then you should be refunded the accommodation charge part of the €150.
You won't be refunded the Airbnb fees or any taxes. For example if the total you were charged was €150 and Airbnb fees of €10 were part of that then you should be refunded €140.
The €15 dredit won't be transferred to your bank account. You never get the credit as real money in your bank account. It stays as a credit in the Airbnb system for you to use the next time you make a qualifying booking.
So in my example I think you should see something like €41 put into your account. That is €140-€99. The €15 credit stays in your Airbnb account.
Hope this helps.
Steve.