What is a German 6th chord? How did it get its name? Is that name even important in any way? First of all, no one, and I really mean NO ONE, has any idea where the label “German” came from. They could have named this chord the Martian chord because the name itself tells us nothing. The 6th label comes from rewriting the dominant 7 interval. That interval becomes what is called a augmented 6th.
The spelling does not change the chord.
If you are reading it, that may give you additional information about where that chord is going to go next. But music is about sound and not about what we see. You should not be using visual clues at all. Musical spelling is for the people who write music. For those who read music we just hope that things were written in the clears possible way.
So the German 6th chord is a bVI7 chord.
It is a half tone above a V7 chord. Then it expands. For instance, if you are in the key of C minor, pick an Ab7 chord instead of a G7 chord. Then you expand it to a C minor chord. That is the whole thing.