If Russia does the West Russia Stack (a VERY sound strategy), then in all honesty… no, Germany cannot counter in Belorussia or West Russia.
The counter is to PREPARE for future combats, and to flank Russia.
The Belorussia/West Russia open creates a thin/vacant Russia position in the Northern axis of attack (Karelia & Archangel). This area allows Germany to re-gain some/all of the IPC losses to Russia in R1, but will be thinly held (though Karelia can be stacked, at the expense of other fronts).
Basically, as Germany, you want to fortify a frontier of Ukraine/Eastern/Karelia as heavilly and as quickl;y as possible. Eastern will be your STRONGEST position, with Ukraine Second and Karelia 3rd. Once you fortify to the point where your Eastern forces can withstand a counter by teh West Russia Stack you move into and re-take Belorussia. This gives you a solid and cohesive 3 territory front versus Russia.
If you want to be daring, take Archangel too to threaten Russia itself, just remember that West Russia can strike Karelia directly.
The better answer is that once you have the K/B/U front fortified… TAKE OUT THE WEST RUSSIA STACK! You can use ALL 3 of your frontal territories for the offensive to take and HOLD West Russia. Then you threaten both Caucuses and Russia, and you attack the weaker territory.
Build INF and ART early, follow up with ARM. Then crack West Russia about G3 or 4.