I want to understand the meaning of Korean idioms.

Hello! I heard a few sentences in Korea, but I couldn't understand them simply through translation, so I'm seeking help. It seems like Korean idioms, and even though I tried Google Translate, the meaning didn't quite come across, so I need a direct explanation. The first sentence is 'If it's time to die, quietly tighten your belt.' The second is 'How sweet a dog's life must be,' and finally, there is the sentence 'Make sure to fall into my hands.' I would like to know in what situations each sentence is used, and why such expressions are used. Is there anyone who can explain these sentences? My Korean friends around me find it difficult to explain easily, so I'm wondering if I can get help here. Thank you!