Do I need to receive any permission to fly in Copenhagen my Mavic Mini? And is there any fee for flying without permission?
I know there is a lot of spot with "High-security level" but I couldn't find any useful info related to MavicMini. Thanks for the help.

You need to read "ByDroneBekendtgørelsen" on https://www.retsinformation.dk/Forms/R0710.aspx?id=194964.This said - with min. a 1A license, you should already be aware of this, and without the license, its a big NoGo!

I have to correct my initial assessment, as it appears to sneak under both current local and upcoming EU regulation, so you should actually be good to go, only governed by common sense.

I see for drone regulation in Denmark . I think this is latest. https://earthofdrones.com/latest-drone-rules-in-denmark/