Learn Hardcore Indonesian: Kalau bukan koordinasi yang bagus, ya jadwal fleksibel yang menyelamatkan kami. - If it isn’t good coordination, then a flexible schedule saves us.

In this line, ya is not "yes." It's a discourse particle roughly meaning "then," "so," or "well," introducing the alternative with a slightly resigned or matter-of-fact tone. You could read it as, "If it wasn't X, then Y (was)." Removing it doesn't change the core meaning, but you lose a bit of that conversational flavor.

Why is it bukan and not tidak?

Bukan negates a noun or noun phrase, while tidak negates verbs, adjectives, or prepositional phrases. Here, koordinasi (yang bagus) is a noun phrase, so bukan is correct. Tidak koordinasi yang bagus would be ungrammatical.

Why are there two yangs, and what do they do?

In koordinasi yang bagus, yang turns the adjective bagus into a restrictive clause: "coordination that is good" (i.e., the good kind of coordination).
In jadwal fleksibel yang menyelamatkan kami, yang introduces a relative clause "that saved us," modifying jadwal fleksibel. So each yang attaches extra information to the noun before it.

Where is the verb or predicate in the first half (Kalau bukan koordinasi yang bagus)? It feels incomplete.

It's ellipsis, which Indonesian uses a lot. The understood predicate is the same as in the second half—something like (yang menyelamatkan kami). Fully spelled out, it would be: Kalau bukan koordinasi yang bagus (yang menyelamatkan kami), ya jadwal fleksibel (yang menyelamatkan kami).

Is ya necessary?

No. You can say Kalau bukan koordinasi yang bagus, jadwal fleksibel yang menyelamatkan kami. Ya adds a conversational "then/indeed" feel. In more formal writing you might see maka or berarti instead of ya.

Can I drop yang in koordinasi yang bagus and just say koordinasi bagus?

Yes. Koordinasi bagus is perfectly fine and common. Adding yang tends to make it more specific/contrastive ("the good kind of coordination" as opposed to other kinds) and a bit more formal-sounding.

Could I use adalah here?

Not as Jadwal fleksibel adalah yang menyelamatkan kami—that sounds awkward. If you want an equative with adalah, flip it: Yang menyelamatkan kami adalah jadwal fleksibel. The original cleft with yang already does the focusing, so adalah is not required.

Can I rewrite the second part without the cleft, as a simple SVO sentence?

Yes: Kalau bukan koordinasi yang bagus, jadwal fleksibel menyelamatkan kami. This is grammatical but slightly less emphatic. The clefted version (… jadwal fleksibel yang menyelamatkan kami) highlights "the flexible schedule" as the specific saver.

What exactly is menyelamatkan? Why not just menyelamat?

The root is selamat ("safe"). With the meN- prefix and the -kan suffix, you get menyelamatkan "to make [someone] safe; to save/rescue" and it takes a direct object (kami). The form menyelamat is not standard; use menyelamatkan (active) or diselamatkan (passive: "to be saved").

How do I mark past/completed meaning here?

Indonesian doesn’t inflect for tense. If you want to stress completion, add an aspect marker: yang sudah/telah menyelamatkan kami. You can also add a time adverbial elsewhere (e.g., kemarin, tadi).

Why kami and not kita?

Kami = "we/us" excluding the listener. Kita = "we/us" including the listener. Since the sentence presumably refers to a group not including the addressee, kami is appropriate.

Is there any nuance between bagus and baik in koordinasi yang bagus?

Both can work. Bagus often evaluates quality or outcome and is common in everyday speech; baik feels a bit more formal and can carry a nuance of "proper/appropriate." In formal writing you might see koordinasi yang baik; in conversation koordinasi yang bagus sounds very natural.

Is kalau the best choice, or could I use jika/apabila?

All mean "if." Kalau is the most colloquial and very common in speech. Jika and apabila are more formal; swapping kalau for jika would make the sentence a touch more formal without changing the meaning.