"I do not sleep yet."
Translation:Tôi chưa ngủ.
Putting chưa at the end makes a question. Your sentence would translate something like Have I slept yet?
Is this correct? : Tôi chưa ngủ = I do not sleep yet Tôi ngủ chưa = Have I slept yet?
bonus. tôi ngủ trưa = I'm taking a (afternoon) nap./I took a (afternoon) nap. "chưa" and "trưa" are not homonymous but would sound really similar to unfamiliar ears.