Translated, can anyone check, I am unsure what Kupa means, I can only guess it's the sound of cum leaking...

くぱー is onomatopoeia. It can mean 'spread pussy,' 'spread anus' or act as a sound effect for the spreading. See post #269209 and post #503365 for other examples, as well as just about every H-manga ever. Unfortunately I can't confidently correct your translation.

Another thing, use tags for your translation notes rather than parenthesis.

Is that Krauss' arm?

yeah most likely

Cleaned up the notes a little.

FYI, "kupaa" usually does mean the vagina, but it can apply to anything moist that's being opened. For example, if someone opens their mouth suddenly, and their lips were moist, it would make a "kupaa" sound.