When you learn a language, struggling with all the grammar issues, you may wonder: can I neglect the grammar, just learn it through sentences or expressions?
The answer is, I strongly believe, NO.
If you just want to know several expressions for traveling or for some casual small talk, then memorizing those a few words is quite enough. However, if you want to understand what Koreans are saying, what your favorite lyrics mean, and/or what characters in a movie/drama are talking about, you have to learn grammar.
Grammar is like a foundation stone. With it, you can easily understand the composition of sentences and expressions.
Don't worry too much about it - take it easy! Let's learn it step by step, and then you will find yourself understanding the Korean language more clearly.