When you are confused in using 은/는/이/가 & 에/에서
When you explain something you need to use 은/는/이/가 for the noun
ex ) 사람은 동물이다 : 은/이 comes after consonant (ㅁ)
ex ) 나는 사람이다 : 는/가 comes after vowel (ㅏ)
When you explain the place where something is being, you need to use ~에
ex ) 내가 사는 곳에 개가 있다 : there is a dog where I live
When you explain the place where something happens/acts, you need to use ~에서
ex ) 내가 사는 곳에서 용이 태어났다 : a dragon was born in a place where I live
Sometimes ~에서 is used for "from"
*you can use ~에 instead of ~에서 sometimes.