My bad Japanese :(
Konnichiwa!
watachi wa Elena desu, --> Watashi wa Elena desu.
demo nihongo ga hiragana/katakana/kanji to yaku dekinai....
--> Mada nihongo ga heta desu. (My Japanese isn't good yet.)
Hiragana to katakana ga wakarimasen. (I don't understand/know hiragana and katakana. = I can't read nor write hiragana and katakana.)
*You don't have to worry about kanji, please learn hiragana first, then katakana, please.
chotto muzukashi desu... --> Chotto muzukashii desu.
Ganbarimasu!!! (Correct!)
Good job! I hope this helps you. Good luck!