这些来自什么作文范文?是学生作文吗?因为你提出的问题的确都是语法错误。第一句,后面的单句主语明显不是和前句相同的I,所以不应该省略。正确写法应该是I have enrolled in a class and hopefully it can improve my skill. 第二句,的确没有to doing sth.作为宾语的用法。正确写法应该是The first one is to raise awareness and to educate people to change the ways they use products.