As long as you are consistent with your pronunciation of the words and use them consistently, german or english, it doesn't make a difference what you say. You can't say one thing half the time and something else the other half - it wont work. I find that it also needs to be said in a similar way each time, so the sound is the same. Bunnies do not want to please us like dogs, they simply choose whether to listen or not.
Although I must say that whilst my buns aren't 'trained', they respond to things I do naturally - so if I bend down to kiss Barney he'll reach up to bump my mouth with his nose, if I open and close my hand exaggeratedly to get his attention he'll usually come over, if I hold my hand in a 'stop' signal in front of him he'll either stop where he is going/won't jump or he'll head-butt my hand to say 'get out of my way', if I make a motion like I'm holding something above him in the air he'll periscope. Barney doesn't respond to verbal commands as he is deaf.
Anna isn't deaf, and she'll come when I call her expecting food, she used to come to a sing-song 'Aaannnabelllllaaaaa' but now I just call 'Anna'. She also knows 'no!', but whether or not she responds to it is a different matter and depends on what she is doing and how much she's enjoying it. And she knows 'No, get down' too.
'Punishing' bunnies or getting them to respond to 'no!' doesn't always work. And it is important that we don't say 'no!' when they are just doing something that comes naturally. For instance, if every time you tried to talk, someone yelled 'no!' at you, you'd be unable to practice that instinctual behaviour to communicate, and if done as a child it would actually stunt your mental development and you wouldn't be able to function normally. We choose to keep the rabbits in an unnatural environment, we can't then insist that they adapt themselves perfectly to that environment.
