まだ〜ていません
Haven't done something yetmachine translation
Formationまだ + verb て-form + いません
Use まだ〜ていません to say "haven't done it yet" — usually as the answer to a もう〜ましたか question (have you … yet?): 「もう食べましたか。」—「いいえ、まだ食べていません。」
A very common mistake among Vietnamese learners: answering with 食べませんでした. That sentence means "(back then) I didn't eat" — a matter already closed, not "I haven't eaten (and may still eat)". The meaning "not yet" requires 〜ていません.
You can also answer briefly: いいえ、まだです (not yet).
Examples
昼ご飯はまだ食べていません。
I haven't eaten lunch yet.
宿題はまだ終わっていません。
My homework isn't finished yet.
その映画はまだ見ていません。
I haven't seen that movie yet.