How do you say senior in Korean languages?

Answer 1

"Sunbae" (선배) in an informal way of saying it.

You can also ad "nim" to make it more formal.

The honorific suffix -님 (-nim) is affixed to many kinship terms to make them honorific. Thus, someone may address his own grandmother as 할머니 (halmeoni) but refer to someone else's grandmother as 할머님 (halmeonim)

Answer 2

You say it like this: Hak-seng (the 'G' is a silent letter)

Korean: 학생

Answer 3

수석 목사 = senior pastor