There are several ways to say thank you in Korean. 감사합니다 is the most polite way and formal way to say ‘Thank you’. 고맙습니다is a little less formal but still polite. 고마워요 is a friendly way to say, so you can use this to a person who are close to you, but not the same age friend. 고마워 is used between friends who are the same age or to a person who is younger than you.
For saying sorry, there are also many ways to say. 죄송합니다 is the most polite and formal way to say ‘I am so sorry’, it is usually to an old person or bosses. 미안합니다 is less formal than 죄송합니다, but it is still polite. 미안해요 is the most common because it is a friendly way to say ‘I am sorry’. You can use this to your generation, but not to elders. Between friends who are the same age, you can say 미안해 which is very casual.
There is one more thing I want to add in this post, which is “Happy birthday!”. It is 생일 축하합니다 or 생일 축하해요 생일 means ‘birthday’ and 축하합니다/축하해요 mean ‘Congratulations’.
The birthday song in Korean is
생일 축하합니다. 생일 축하합니다. 사랑하는 ㅇㅇㅇ(name), 생일 축하합니다.
You can sing this song for your Korean friends! You can click a link below to listen to the full song.