Words that easily remember is basic word like :
Thank you = Gamsahamnida (formal) / Gomawo (Informal)
Sorry = Chesoenghamnida (formal) / Mianhae (Informal)
What are you doing? = Mohae (Informal)
Are you okay? = Gwenchanha
Love you = Saranghae
Those are in Korean.
I love you in other language
Airishiteru (Japanese)
Rak rak (vietnamese?)
Tia mo (Spanish?) ← I learn it from Dora the explorer.
Aku cinta kamu (Indonesian)
Wo ai ni (Chinese)