One, Korean Republic only has Korean Language widely spoken in their own country. That does not include dialects spoken.

It's "Sa rang he" or if you want it in Korean words it's "사랑해"

To say lucky in Korean, one can say un-i joh-eun. This is the colloquial or informal way of saying lucky. The Korean language, however, has a wide variety of dialects and levels of formality.

The twelfth largest spoken language in the world--according to the Ethnologue--is Wu, one of the dialects of Chinese spoken largely in the south. Not accounting for dialects, the answer would be Korean.