北京的B要大写
He is of medium build and he is of medium height比较绕口,可改为He is of medium build and medium height.
hobbys改为hobbies
His hobbys are playing the violin and playing sports.He is very good at swimming and playing volleyball.过于绕口,(且有语法错误,可改为He likes piaying the violin and doing sports .He is good at swimming and playing volleyball .
仅供参考