For me it also sounds strange...For example, a teacher talking to her pupils: - ¿Habéis hecho ya el ejercicio? ¡Qué rápidos! - ¿Todavía no habéis terminado? ¡Sois más lentos que las tortugas! I hope it helps, just my two cents. David C.

It depends on the context. Usually "todavía" means "still" (I still haven't done my homework, "Todavía no he hecho la tarea"). "Ya" could also mean "todavía" ("I haven't told you just yet", "Todavía no te lo dicho"), and "already" could also mean "ya" ("I have already told you", "Ya te lo he dicho"). It can be confusing, maybe this will help -> http://www.isabelperez.com/Already%20Yet%20Still.htm