Alright i found my solution:
WidevineCdm still doesn’t PopUp to install it on Amazon.de ! So i went to Spotify.de -> there it shows me to install WidevineCdm and i installed it.
Yet Videos wont work on Amazon. Just loading and a error PopUp with “Video not available”.
You have to turn off Adblock. And now it works.
Just for people who have the same issue.
Now i will love this Browser :]
[Sorry for my English. It’s my teacher’s fault /Kappa]