Learn Hardcore Hausa: Kar ku kashe fitila kafin mu gama karatu. - Don’t turn off the lamp before we finish studying.

Together, kar ku means “you (all) must not / don’t (you all) …”.
So kar ku kashe fitila literally means “don’t you‑all turn off the light.”

Is there any difference between kar ku and kada ku?

Both kar ku and kada ku mean “you (all) should not / don’t (you all)”.

kada is the full, more formal/standard form.
kar is a shortened, very common spoken form.

In writing (especially formal texts), kada ku kashe fitila… is more typical.
In everyday speech, you will hear kar ku kashe fitila… all the time.
There is no difference in meaning, only in style/feel.

Why does kashe mean both “kill” and “turn off”? Isn’t that confusing?

Kashe basically means “to kill / to extinguish / to put an end to something.”

With people/animals: kashe mutum = to kill a person.
With fire/light/electricity: kashe wuta / kashe fitila = to put the fire/light out.
With devices: kashe waya = to switch off a phone.

Many languages use the same verb for “kill/extinguish/turn off”.
Hausa speakers understand the meaning from context:
in kashe fitila, nobody thinks of killing; they understand “switch off / put out the light.”

What exactly does fitila mean? Is it only “lamp,” or any kind of light?

Fitila is a light source: lamp, bulb, flashlight, lantern, etc.

It can refer to:

an electric bulb or room light,
a kerosene lamp,
a flashlight/torch,
depending on context.

If you want to talk about light in general as a phenomenon, you’d more likely use haske.
Here, fitila is the physical thing you can turn on/off.

How is the negative command built here? What is the basic pattern?

The basic pattern for a negative command in Hausa is:

kar / kada + subject pronoun + verb (+ objects)

So in this sentence:

kar – negative imperative marker (don’t)
ku – you (plural)
kashe – turn off
fitila – the light

Kar ku kashe fitila = “Don’t you‑all turn off the light.”

For a positive command to several people, you drop kar/kada and just say:
Ku kashe fitila = “Turn off the light (you all).”

Why is it kafin mu gama karatu and not kafin mun gama karatu?

Kafin (“before”) normally takes a subjunctive verb form, because it refers to an event that has not yet happened at the reference time.

mu gama is subjunctive: “(that) we finish.”
mun gama is perfective (past/completed): “we have finished / we finished.”

So:

kafin mu gama karatu ≈ “before we (will) finish studying/reading.”
kafin mun gama karatu would be used in a past narrative, like:
Kafin mun gama karatu, ya kashe fitila.
“Before we had finished studying, he turned off the light.”

In an instruction like your sentence, you want the subjunctive mu gama, not mun gama.

What does karatu mean here? Is it just “reading,” or “studying,” or “lesson”?

Karatu is a verbal noun from karanta (to read), and it covers a range of meanings related to reading and study:

reading (of a text),
studying (school work, learning),
schooling / education in some contexts.

In mu gama karatu, the meaning is “finish our studying / reading (lesson)”.
Depending on the situation, you might translate it as either “reading” or “studying.”

Could I say something like kafin mu gama karantawa instead of kafin mu gama karatu?

You could see forms like karantawa, but in this common collocation, gama karatu is the natural, idiomatic phrase.

gama karatu is a very standard expression: “finish studying / finish one’s studies / finish reading.”
karantawa is another nominalized form from karanta, but it is less usual here and would sound odd in everyday speech in this specific phrase.

So for this sentence, you should stick with kafin mu gama karatu.

How would the sentence change if I were talking to just one person instead of several?

For one male:

Kar ka kashe fitila kafin mu gama karatu.
(ka = you, masculine singular)

For one female:

Kar ki kashe fitila kafin mu gama karatu.
(ki = you, feminine singular)

For several people (mixed or all male/all female), your original sentence is correct:

Kar ku kashe fitila kafin mu gama karatu.

Can I drop the mu and just say kafin gama karatu?

You will most naturally say kafin mu gama karatu. Dropping mu changes the feel:

kafin mu gama karatu – “before we finish studying” (clear subject: we).
kafin gama karatu – sounds like “before finishing studying” in a more impersonal / generic way; it is possible in some contexts, but here it is less clear who is finishing.

If you want an impersonal subject (like English “before the studying is finished”), you might hear:

kafin a gama karatu – literally “before one/they finish studying.”

For your intended meaning, kafin mu gama karatu is the best choice.

Can kafin mu gama karatu go at the beginning of the sentence instead of the end?

Yes. You can say:

Kar ku kashe fitila kafin mu gama karatu.
Kafin mu gama karatu, kar ku kashe fitila.

Both are correct and mean the same thing.
Putting kafin mu gama karatu first just highlights the time condition (“Before we finish studying…”) and then gives the command.

How strong or polite does kar ku kashe fitila sound? Is it rude?

Kar ku kashe fitila by itself is a direct, clear command, but not automatically rude.
It’s like saying “Don’t turn off the light” in English with a neutral tone.

To make it softer / more polite, you can add expressions such as:

Don Allah, kar ku kashe fitila kafin mu gama karatu.
(“Please, don’t turn off the light before we finish studying.”)

Tone of voice and context matter a lot; grammatically, the form is just a normal negative imperative.