Hi Xiaoxu193! Thanks for contributing to Wikipedia. Be our guest at the Teahouse! The Teahouse is a friendly space where new editors can ask questions about contributing to Wikipedia and get help from peers and experienced editors. I hope to see you there! SarahStierch (I'm a Teahouse host)
Xiao, when you respond to someone in a talk page, it is a standard that you use indentation. Use a colon : at the beginning of the paragraph to create the indentation.
For example, this indent is a response to the previous paragraph.
And this indent is a response to the second paragraph.