아/어서 grammer sentences

오늘 눈이 와서 학교에 안 가고 싶었어요.
--- Today it was snowing so I didn't want to go to school. (o) perfect

저는 심심해서 친구들하고 영화를 보고 싶어요.
---I want to see a movie with my friends because I am bored.  
제 친구들이 많이 와서 파티가 재미있었어요.
--- The party was fun because many of my friends came.

공부를 해야 해서(or공부를 할 필요가 있어서) 도서관으로 갈 거예요.
--- I'm going to the library because I need to study.

제 아파트가 더러워서 내일(you don't need to put 은) 청소할 거예요.
--- I'm going to clean my apartment because it is dirty.

(and technically you need to put 내일 제 집을 or 제 아파트를 because 제 아파트가 is a subject and you need to something to clean. it's a object. but i think you don't need to say it in conversation.)

and it's a private thing. i really care about grammar of Korean when i'm saying

but i don't even know proper usage of ~에요 and ~예요. it is really complicated even for native Korean. So what i wanna say you don't need to care much about ~에요 and ~예요.