How do you say “Let me know.” in Korean?

= (polite) 알려 주세요. [al-lyeo ju-se-yo.] / (casual) 알려 줘. [al-lyeo jwo.]

How do you say “Never mind.” in Korean?

= 아니에요. / 아무것도 아니에요.

[a-ni-e-yo.] / [a-mu-geot-do a-ni-e-yo.]

How do you say “He is out of town.” and "He is not in the office." in Korean?

= 지금 (__any city name__)에 안 계세요. [ji-geum (__any city name__)e an gye-se-yo.]  

지금 사무실에 안 계세요. [ji-geum sa-mu-si-re an gye-se-yo.]

How do you say “My job is my first priority.” in Korean?

= 일이 최우선이에요. / 저는 일을 최우선으로 생각해요.

[i-ri choe-u-seo-ni-e-yo.] / [jeo-neun i-reul choe-u-seo-neu-ro saeng-ga-kae-yo.]

How do you say “Just because!!!” in Korean?

= 그냥!!! [geu-nyang!!!]