Hi, Andrea. Sentences 1, 2, 3, and 4 sound good. Perfect. In 5, we usually use 거두다 or 걷다(short for 거두다) as Andrew suggests. So, I would say 내일 (여러분의) 숙제 걷을 겁니다 if I were a teacher speaking to my students. Sentence 6; I would say 빨리 니 소지품 챙겨. 챙기다 sounds more natural in that kind of situation. Extra tips; 우리 돈모아서 아빠 생일선물 사자. In this sentence, 모으다 means to chip in. Hope this helps.

1) 저는 돈을 모아요. I am saving money. --> I save (my) money. 2) 저는 돈을 모으고 있어요. I am saving money. 3) 제 친구는 우표를 모아요. My friend collects postage stamps. 4) 가난한 사람들을 위해서 우리는 음식을 모아요. We are collecting food for the poor. --> we collect food for the poor. 5) (선생님이 학생들에게 말하다) 내일에 저는 그들의 숙제를 모을거 예요. (A teacher saying to the students) I will collect your homework tomorrow. Quick Correction: (선생님이 학생들에게) 내일, 저는 여러분의 숙제를 걷을 거예요. Translation : (From teacher to student) Tomorrow, I will collect your homework. 모으다 turns into "gather up" when you try to use the word in this sentence. It would be like saying "Tomorrow, I will be gathering up your homework." 6) 빨리 너의 소지품을 모아. 우리 늦어. Hurry up and gather your things. We are late. Quick Correction : English translation is a bit off. Hurry up and gather your belongings; we will be late. Please leave me more examples if you can think of any common examples. I hope this helps! Leave a comment if you have more questions.