오늘은 I’ll be telling you the secret of why Koreans drop things like subjects, topics, particles, etc. when talking and how to know when to do

Here I have listed out some difference and rules for 은/는 & 이/가. There's also a particles quiz at the end of the lesson.

-에 and -에서 both mean the same thing, but they have different usages and rules. This post is a very simple explanation plus a short practice.