Wakarimasu ka? Do you understand?

Konnichiwa!
Watashi no namae wa Kai desu. Watashi wa igirisu ni sundeimasu. Watashi wa gakusei desu.

Itsuka nihon wo otozure tai desu(or nihon ni ikitai desu). Watashi no nihongo wa heta desu. Nihonn go wo renshuu suru hitsuyou ga arimasu. Watashi wa mada roma-ji shika wakarimasen.

Hello!
My name is Kai. I live in England. I am a student.

I like Japan. My Japanese is bad. I need to practise my Japanese. I'm sorry I only know romaji yet.

Hi, great job! There are small errors but we understand what you wanted to say without problem. Please learn step by step. If you gave doubt in my corrections, please let me know. I hope this helps you.