Learn Hardcore Swahili: Nilikuwa nimekosea ishara kwenye ramani, lakini sasa nimezisahihisha. - I had gotten the symbols on the map wrong, but now I have corrected them.

It’s the Swahili past perfect (pluperfect). Nilikuwa nimekosea means “I had made a mistake,” i.e., the mistake happened before another past reference point. Compare:

Nilikosea = I made a mistake (simple past).
Nilikuwa nimekosea = I had made a mistake (earlier past).

Could I just say Nilikosea ishara kwenye ramani instead of Nilikuwa nimekosea ishara kwenye ramani?

Yes, but it changes the timing. Nilikosea… states a past event. Nilikuwa nimekosea… anchors that mistake as completed before another past context (which here is contrasted with “but now…”).

Why is there a zi- in nimezisahihisha?

zi- is the object marker agreeing with a plural noun in class 10. Ishara belongs to noun class 9/10; in the plural it takes class 10 agreement, so the object marker is zi-: ni-me-zi-sahihisha = I-have-them-corrected.

How do I know ishara is plural here when the word itself doesn’t change?

Class 9/10 nouns (like ishara) often have identical singular and plural forms. The agreement tells you the number:

Singular: object marker i- → nimei…
Plural: object marker zi- → nimezi… Here, nimezisahihisha shows it’s plural (“them”). You can also mark it explicitly as ishara moja (one symbol) or ishara nyingi (many symbols).

Do I have to use the object marker? Could I say Nimesahihisha ishara?

You can drop it: Nimesahihisha ishara is grammatical. Using the object marker (nimezisahihisha) is preferred when the object is specific/known (“those symbols we mentioned”) and makes the sentence more cohesive. Both together (Nimezisahihisha ishara) is also common for emphasis or clarity.

Why use kwenye with ramani? Could I use katika or juu ya?

kwenye ramani = on/in the map (very common, neutral).
katika ramani = in the map (a bit more formal/literary).
juu ya ramani = on top of the map (physical position on its surface).
For “map symbols,” kwenye (or katika) is the usual choice.

Is ishara kwenye ramani the most idiomatic way to say “map symbols”?

It’s fine, but many speakers would say alama za ramani or ishara za ramani (“symbols of the map,” i.e., the map’s symbol set).

…kwenye ramani = symbols that appear on a particular map.
…za ramani = the conventional symbol system used by/for maps.

What’s the difference between kosea and kosa?

kosea = to be wrong about/do something incorrectly in relation to X: kosea ishara (get the symbols wrong).
kosa = to err/miss/lack; depending on context it can mean “make a mistake,” “miss,” or “lack.” Saying kosa ishara tends to mean “miss the symbol(s).” For “get the symbols wrong,” kosea is the natural choice.

Could I rephrase with “mistakes” as nouns?

Yes: Nilikuwa nimefanya makosa kwenye ramani, lakini sasa nimeyarekebisha/nimeyasukurupua?
Better: …nimeyarekebisha or …nimeyasahihisha. Note the class 6 object marker for makosa (class 6 plural): ya- → nimeyarekebisha.

What exactly is inside nimezisahihisha morphologically?

ni- (subject “I”)
-me- (perfect aspect “have”)
-zi- (object marker for class 10 plural “them”)
sahihish- (verb root “correct/fix/make right”)
-a (final vowel)

Why use nime- after sasa? Could I use a simple past?

Sasa nimezisahihisha highlights a present-result: “now I have corrected them (and they’re correct now).” You could say sasa nilizisahihisha but it sounds like you did it in the past without emphasizing the current result. With sasa, nime- is most natural.

Can the position of sasa move?

Yes. Common options:

…, lakini sasa nimezisahihisha.
…, lakini nimezisahihisha sasa.
The first feels a bit more natural, but both are fine.

Are there alternatives to sahihisha?

Yes:

rekebisha = fix/adjust/correct (very common and broad).
hariri = edit (texts). In this sentence: nimezirekebisha works well too. sahihisha leans toward “make correct.”

What if I corrected only one symbol?

Make agreement singular:

Nilikuwa nimekosea ishara moja, lakini sasa nimeisahihisha.
Note the singular object marker i- in nimei-… for class 9 singular.

How would I say “but now I haven’t corrected them yet”?

Use the negative perfect -ja- and keep the plural object marker:

Lakini sasa bado sijazisahihisha.
For the earlier clause in the negative pluperfect: Sikuwa nimekosea = I hadn’t made a mistake.

What’s the difference between Nilikuwa nimekosea and Nilikuwa nakosea?

Nilikuwa nimekosea = I had already made a mistake (completed before another past point).
Nilikuwa nakosea = I was making mistakes/was in the process or habit of making mistakes (past progressive/imperfective).

Any nuance between lakini, ila, and bali?

All can translate as “but,” but:

lakini = general-purpose “but.”
ila = “but/except,” very common in speech.
bali = “but rather,” used for corrections/contrasts: Sikukosea ishara, bali ramani yenyewe.

Is the comma before lakini required?

It’s optional but common, just like in English. You’ll often see …, lakini … to mark the contrast.

Could I say Nimekosea by itself to mean “my bad”?

Yes. Nimekosea is often used as “I’ve made a mistake / my mistake,” especially when apologizing or acknowledging an error.