The trannslation of minor and major sixth as moll (minor) and Dur (major) seems to me a bit misleading since minor and major refer primarily on the size of an interval, while “Dur” and “Moll” refer on the harmonic tonality.
This could be imho a bit misleading, since for instance the major (large/große) third of a major (Dur) chord or scale is in its inversion a “minor” (small/kleine) sixth meanwhile the major (Dur) chord remains in his first inversion still a major chord and is not at all hamonicly “minor” (moll) even when his “major” (large/große) third becomes a “minor” (small/kleine) sixth.
Maybe it would be at least for the german translation better to use the terms “groß” (major) and “klein” (minor) as we are more familiar to apply them especially on the sixth interval meanwhile it seem to me still for both sixth and third the correct translation for “major”(groß) and “minor” (klein) intervals.
Just an Idea…