GSD's do play rough and sound like they are murdering each other. Generally, if I pay attention and start being able to pick up on 'normal' and 'over the top'. It can quickly get too much, especially at that young age when they are testing the waters.
If I start feeling uneasy, I'll break it up with a quick run for treats or petting and some loving just to break the possible tension.
MACH3 Bretta Lee Wildhaus MXG MJG MXF MFB TQX HIT CGC TC
Glory B Wildhaus AX, AXJ, XF
"Behind every great man is a woman rolling her eyes." - Jim Carrey