Still v/s yet v/s already:
1. Still - used to talk about something that hasn't finished especially when it was expected to finish earlier.
- used in questions, affirmative and negative sentences
He is still angry at his best friend.
Are you still smoking? I though you had quit.
2. Yet - used to talk about something which is expected to happen
- used in questions and negative sentences.
Have you written the report yet?
She hasn't finished her homework yet.
3. Already - used to talk about something that has happened, often earlier than expected.
- used in affirmative sentences and questions
I already know what I will buy you for your birthday.
Has he already left the party?