In Heidegger's terminology "das Sein" ( the being, as in continued existence) refers to the experience and understanding of a creature, that is to say that my being has enabled me to understand the world. "Das seiende" ( the being, as in the thing that is) refers to the physical reality of things and beings in our world, that is to say that the being(s) surrounding shape my understanding of the world.
In the quote about the German language - which by the way nobody seems to be able produce in the German original, making it likely to not be an authentic and singular quote - may allude to his belief (?) that the German language is either better suited to or more often used to relay existential experiences, rather than mundane facts of physical existence. But take this with a grain of salt. I'm a German tutor, not a nietzschean philosopher... ;)
HTH
Armin
