Nakereba narimasen!
Konnichiwa minasan!
Watashi wa "nakereba narimasen" wo wakarimasu demo... watashi wa eigo wo hanashimasu, nazenara watashi no nihongo wa totemo warui desu! >.< Sumimasen!
I mean, I understan how to use "nakereba narimasen" such as: i must... but i don't know how to say: I mustn't~
What's the form? "Nakereba narimasen" is a double negative form, isn't it?
Arigato gozaimasu anatatachi no tetsudai >.<