Form and rules
How it works
Already usually means earlier than expected and often comes before the main verb or after be: I've already sent it; She's already here.
Yet usually appears at the end of questions and negatives: Have you finished yet? I haven't finished yet.
Still means a situation continues and normally comes before a main verb but after be: I still work there; I'm still waiting.
Still not emphasizes continued absence/non-completion: They still haven't replied.
Already can appear in questions to express surprise: Have you finished already?