New key for RotTR: DE but how can i add it to giveaway

You can't add it if the giveaway already started, you can if you delete the giveaway and make a new one with all the keys.

You can edit the key when the GA ends.

A second key for a second winner I dont think is possible, so new giveaway :)

You just create some record in SG. There is thousand entry for 1 hour GA...
Key come out from nowhere and People come out of nowhere