TADI is used before the words PAGI, SIANG, SORE, and MALAM to mean past time within the span of the day, while NANTI is used before SIANG, SORE, and MALAM to refer to the corresponding future time.
Where should be expressed as kemana, dimana, or dari mana depending whether it is 'to where','at where' or 'from where'. Kemana = to where Kemana anda pergi? (where do you go?) Dimana = at where Dimana dia tinggal? (where does he live?) Dari mana = from where Anda dari mana? (where do you come from?)
SUDAH indicates that an action has been completed while BELUM denotes that it has not been completed or has not taken place. MASIH shows that an action has taken place but has not been completed.
SEDANG is only used to demonstrate that an action is/was progressing or is/was being carried on. Saya sedang makan. (I'm eating) Adik sedang belajar. (Brother is eating)
Maaf means sorry and it used when asking to be excused for imposing on someone or for something one has failed to do. It can also mean excuse me when used before requesting information.