You can say...
私の日本語が上手じゃありません。
Watashi no nihongo ga jyozu ja arimasen.
(My Japanese is not good.)
Or...
私の日本語が下手です。
Watashi no nihongo ga heta desu.
(My Japanese is bad.)
Since the Japanese culture is very humble, you could say
まだまだ日本語をもっと勉強しなくちゃいけません。
Mada mada nihongo wo motto benkyo shinakucha ikemasen.
(I still need to study more Japanese.)
Hope this helped :)
-.- I can speak Japanese and you don't say it any differently really, except for maybe the accent I suppose.
You may say 'imouto.'
It's highly unlikely. She said that her parents came from Korea. My friends say that you can see her Japanese-speaking translator tailing after her.
Japanese just use kodomo as in child
I speak a little Portuguese = eu falo um pouco de português.
patty o hanasitakereba ka?
'(person) ni hanashitai n desu kedo.'
he speak English and Hawaii, even he is Japanese, but he can't speak Japanese
chotto or sukoshi if you are talking about the type of little where you say 'a little bit' if you mean the opposite of small, then it's something else entirely.
nihongo wo hanasu koto ga hoshii
You may say 'imouto.'
Ko-Nenko desu ne?