Hi, Yejin Song. Actually, the meaning of the two words in each line are interchangeable. “sesungguhnya - sebenarnya” Both are interchangeable in a text because they have the same meaning. It is the same for “saat - ketika”. The words are interchangeable. Example: Dia datang saat saya sedang makan. Dia datang ketika saya sedang makan. She came while I was eating. As for, “bila/ kapan” if it is regarding of asking about time (WHEN). Bila - kapan are quite different in term of commonly and uncommonly speak in Indonesia. Kapan is more common if you are asking about time. -kapan kita bisa makan? -when can we eat? Bila, in my opinion is used in a poetic text and rarely used in Bahasa Indonesia. In addition, it is a Malay language of “Kapan” “When”. Wish you can get the point of my explanation. If you do have question, feel free to ask me.