Maybe not very consistently, it's kind of a mess. I use "nein" in a few situations:Are you following through with some type of correction?
1. loose-leash walking if he starts pulling or won't leave a smell when I want to go.
for pulling, I say, "nein," pause, and if he doesn't back off (usually doesn't when he's in this mode), give him a sharp upwards jerk.
for leaving-a-sniff, I say, "let's go," and if he doesn't come (often he won't), I say "nein." I've noticed that usually he does leave the sniff at this point, which tells me he does understand the word, at least in this context. I should mention that Jupiter is a quite hard dog, and requires a fairly savage correction to really get a reaction out of (one reason I began to invest heavily in positive training during walks).
2. when we play frisbee, he brings it back, stops about 6 feet away, and drops it. Then he does this thing I hate, he grabs the (flexible cloth) frisbee in the center, which punctures it and rips up grass. If I say "nein" here, he ignores me, so I only get it by grabbing his collar, pulling him up, and saying "drop," which he obeys fairly shortly.
3. general purpose "nein" is usually ignored, it seems. "leave it," which he learned while very young, oddly seems to have better reactions.
4. I should note that I taught both of these commands initially positively, with a treat (he's very food-oriented) after he looks up, but also with a prong correction. The prong correction usually only happens on the walk, but I do give him a treat when he complies and comes back to me.