I've answered the same question before but I'm too lazy to find it so I'll leave a quick answer here. You can use 때문에 with a noun, for example: 비 때문에 못 가요. I(or we) can't go because of the rain. 너 때문에 여기 있는 거야. I'm here because of you. If you use 때문에 with a verb, you'll sound like you're reading a book. -서 is a most comonnly used "because", -하니까 is an emphatic "because". A : Why are you leaving early? B : 몸이 안 좋아서요. Because I'm not feeling well. A : Why are you staying away from me? B : 냄새나니까! Because you smell bad!

때문에, 서, and 하니까 are usually used in this form; (cause) [때문에, 서, 하니까] (outcome) those three words are used to express the cause of the case/ fact in various situations it is really hard to make difference in using of those words..(hoping this answer will be helpful to U)