I don't know how to use "better" in a way it's used in this sentence and what it means. So, does adjective come after "better" and nothing before it?
Answer from a Native speaker
So, here, the subject is implied before "better!" Here it would be: "You better hurry!" Sometimes in conversation and informal English, the subject is omitted since it is implied in the context. The meaning of "better" in this sentence is similar to "you should" or "it would be wise to," "wisely." Implying that the outcome would be in their best interests. And if they didn't do this thing, then there would be some kind of consequence. Ex: You better hurry, or we'll be late. Ex: The movie better start on time. Otherwise, I'll fall asleep during it since it'll be so late. Ex: She better improve her grades soon.