read the humble bundle warning that i can´t redeem the gift, go back to steamgift and read your discription that the game can´t be activated in Germany -> start wondering why you created this giveaway as Region Restricted for Germany, what means that only people from Germany can enter your GA but can´t receive it...
To make it short, i wont be able to use the key so you can contact the support to request a new winner, but i think any other person who entered this GA will have the same problem because of your Region Restriction