Nihongo-wo Nnaratteimasu.

*We use the particle "wo" after the object and "-" isn't needed before "wo". 

Minna-san, konnichiwa! Watashi no namae wa Leora desu. Ni ji kan nihongo-wo naraimasu., Demo sensei wa chyotto warui desu. -__- dakkara jibun (de?) nihongo wo naraimasu!

I would say:

Nihongo wo naratte imasu. 

Minasan, konnichiwa. Watashi no namae wa Leora desu. Ni ji kan nihongo wo narai mashita. (?) 

*(?) two hours a week? Or you have learned it for two hours and now you stop taking the class? We have to change the sentence depends on the situation.) Demo yoi sensei de wa arimasen deshita. Dakara dokugaku de nihongo wo benkyou shite imasu. 

*learn by oneself = dokugaku de benkyou simasu 

Good job! Please enjoy learning. I'd like to suggest you to learn the Japanese characters, hiragana and katakana first if you want to keep studying Japanese. Good luck!