OK, class this week we should do the meat of the lesson in
https://www.howtostudykorean.com/unit1/unit-1-lessons-1-8/unit-1-lesson-2

We have a new particle, ~이/가, which lack the connotation of ~는/은, indicating a contrast with something else. It is also used to indicate a sense of place with the verb 있다 and the particle ~에 on the object to indicate being "at" or going to a time or place. 있다 also means "to have" when ~이/가 is used on the *object*. Whew!