さん(san) is used for both male and female names. くん　is used for only male names. Both san and kun are suffix to call honorifically. ちゃん(chan) is used for both male and female almost chidren's names to call friendly.

"san"= is word both used for male and female. Object is children, young and adult. We will use when we wanna understand as a human being. "kun"= is used when call to boys. It use for from little boys to young men. "chan"= is used when call to girls. It use for from little girls to young girls.

hello，i am from China ,i also study korean .we can study together and help each other. And i like to make diffident friends .

ありがとうございます。

We normally use "san" by default. If you want to refer to the children: [Boys] 1 ~ 5 years old, "chan" 6 ~ before getting employed, "kun" [Girls] 1 ~ 12 years old, "chan" 13 ~ , "san" [Adult] all "san" The border between ages is approximate. However, there are some exceptions. If they are younger family or younger relatives, or you feel them as if your family, you can use "kun" to male, and "chan" to female.