how to get one copie free for Mediterranea Inferno?

how?

https://www.steamgifts.com/about/guidelines

User Content - item 12
Begging. Do not ask game developers or users for keys or games, unless they are offering and searching for interested parties.

Try your luck
https://www.steamgifts.com/game/RYbAm/mediterranea-inferno/open

I don't believe the game is available for free anywhere. You can enter giveaways here and try to win a copy. If you are wondering why so many people are giving it away here, it is because it was in last months Humble Choice.
https://www.steamgifts.com/discussion/Hj3qx/humble-bundle-may-2024-humble-choice-54-loddlenaut-sea-row-out-of-stock

You can find out where giveaway copies of games are coming from here, either by checking for a relevant post or asking yourself if it isn't mentioned by others.
https://www.steamgifts.com/discussion/EhJvw/where-are-those-giveaways-coming-from