Learn Hardcore Indonesian: Jika sinyal buruk, kami melanjutkan belajar tanpa video. - If the signal is bad, we continue studying without video.

jika: more formal/neutral (common in writing and careful speech).
kalau: most common in everyday conversation.
bila/apabila: formal/literary; bila can also sound Malay-ish. Examples:
Kalau sinyalnya jelek, kita lanjut belajar tanpa video. (casual)
Jika sinyal buruk, maka kami melanjutkan belajar tanpa video. (formal; maka is optional)

Is the comma after the if-clause required? Can I switch the clause order?

Yes, put a comma when the if-clause comes first: Jika ..., kami ...
You can reverse the order and usually drop the comma: Kami melanjutkan belajar tanpa video jika sinyal buruk.

Does sinyal specifically mean cell signal, or can it mean internet connection?

Sinyal is a general “signal” (cell/network). For internet quality people also say:

koneksi (connection)
jaringan (network)
internet (the internet) So you might hear: Kalau koneksi buruk/jelek, ... or Kalau jaringan lemah, ...

Is buruk the best adjective here? What about jelek, lemah, or lambat/lemot?

buruk: bad (more formal/neutral).
jelek: bad (very common, casual).
lemah: weak (strength of signal/bars).
lambat/lemot: slow (speed). Lemot is colloquial. Choose based on what’s wrong:
Strength: sinyal lemah
General quality: sinyal buruk/jelek
Speed: internet lambat/lemot

Why not sinyalnya buruk or sinyal yang buruk?

sinyal buruk: general description (a bad signal).
sinyalnya buruk: “the signal is bad” (definite, known signal).
sinyal yang buruk: “the signal that is bad” (more specific/emphatic). All are grammatical; choose for definiteness/emphasis. For a general rule, sinyal buruk is fine.

Should it be kami or kita?

kami: we (excluding the listener).
kita: we (including the listener). Use kami if telling a third party about your group. Use kita if you include the person you’re speaking to (e.g., addressing the class): Kalau sinyalnya jelek, kita lanjut belajar tanpa video.

Does the sentence mean “we will continue” or “we continue”? Do I need akan?

Indonesian has no tense inflection. Context decides:

Habitual/general rule: your original sentence works.
Future/plan: add akan: Jika sinyal buruk, kami akan melanjutkan belajar tanpa video. Both are natural.

Is melanjutkan belajar correct? I heard melanjutkan takes a noun.

It’s common and acceptable. Melanjutkan is transitive and often takes a noun (e.g., melanjutkan pelajaran/kelas), but verbs can function like gerunds, so melanjutkan belajar ≈ “continue studying.” Alternatives:

terus belajar (keep on studying; very natural)
melanjutkan pelajaran/pembelajaran/kelas (continue the lesson/learning/class) Avoid: melanjutkan untuk belajar (unnatural).

What’s the nuance difference among melanjutkan, meneruskan, terus, and tetap?

melanjutkan: continue/proceed to the next part; resume.
meneruskan: continue/carry on; also “forward/pass on” (a message).
terus: keep on/continuously (adverb or colloquial verb).
tetap: still/nevertheless (emphasizes persistence despite a condition). In context:
Kami terus belajar (we keep studying).
Kami tetap belajar tanpa video (we still study, even though video is off).

Can I say lanjut belajar instead of melanjutkan belajar?

Yes, in casual speech: kita lanjut belajar tanpa video. As a command: Lanjutkan belajar tanpa video (formal imperative) or Lanjut belajar tanpa video (casual).

Why tanpa and not tidak or bukan?

tanpa = without (preposition before a noun): tanpa video.
tidak = not (negates verbs/adjectives).
bukan = not (negates nouns/pronouns). So only tanpa fits here. You can make it definite with videonya if you mean “the video [we usually use].”

Is tanpa menggunakan video better than tanpa video?

Both are correct. Tanpa video is shorter and perfectly natural. Tanpa menggunakan/memakai video is slightly more formal or explicit (“without using video”).

Can I move tanpa video elsewhere in the sentence?

Yes, but keep it near the verb phrase:

Natural: Kami melanjutkan belajar tanpa video; Kami, tanpa video, melanjutkan belajar (the second is more written/formal).
Less natural: Kami tanpa video melanjutkan belajar (can sound stilted in speech).

Should I ever use adalah here (e.g., sinyal adalah buruk)?

No. Adalah is used before nouns, not adjectives. Say Sinyal itu buruk or Sinyalnya buruk, not Sinyal adalah buruk.