Not german per se, but german is my main language. I live in austria
I haven't done any DX12 coding, just a little OpenGL sometime ago, but from what I read up on, it's harder to code. You don't have the driver to do everything for you - but then again, many games that use engines like Unity, Unreal or similar won't have to bother with it.
Yes, it will mostly help CPUs with many cores, but still should work quite fine, due to the DrawCallScheduler (the thing that says the GPU what to render next) being not limited to one CPU-core any more, that has to do all the work, but rather all CPU-cores can schedule DrawCalls.
I mean: The i3 got ~30% boost in Ashes. And it will most help in CPU-bound scenes - not GPU-bound.
It's gonna be great, but do you want to hear, what I'm personally really hyped for? Vulkan. Which is practically DX12 but open-source as far as I know.