Hello, my name is...
私の名前は…です(Watashi no namae wa ...des)。
*If you want to say "nice to meet you" instead of "hello", it's はじめまして (Hajimemashite).
I am .. years old
I live in .. (country)
…に住んでいます (...ni sunde imas)。
My hobbies are..
趣味は…です(Shumi wa ...des)。
*Once you mentioned the subject of the sentence (I=私は), you don't have to repeat it until the subject is changed. It's Japanese way.