Learn Hardcore Croatian: Nisam sigurna je li moj naglasak prirodan, ali ljudi me razumiju. - I female am not sure whether my accent is natural, but people understand me.

Nisam already tells you it’s 1st person singular (I).
So Ja nisam sigurna is possible, but Nisam sigurna is more natural unless you want to emphasize I (as opposed to someone else).

What exactly is nisam? Why not ne sam sigurna?

Croatian forms negatives of the verb biti (to be) by fusing ne + the verb:

ne + jesam → nisam (I am not)
ne + jesi → nisi (you are not)
ne + jest → nije (he/she/it is not)

So nisam is the normal, correct negative form of jesam.
You never say ne sam sigurna; it’s always nisam sigurna.

Why is it sigurna and not siguran?

The adjective must agree with the gender of the speaker:

siguran – masculine (a man speaking: Nisam siguran…)
sigurna – feminine (a woman speaking: Nisam sigurna…)

So the sentence as written implies the speaker is female.
Everything else stays the same if a man says it; only sigurna → siguran changes.

What does je li mean, and why is it two words?

je li is a two‑word particle used for yes/no questions. In this sentence it introduces an indirect question:

Nisam sigurna je li moj naglasak prirodan
= I’m not sure whether my accent is natural.

In a direct question, you can put it at the start:

Je li moj naglasak prirodan? – Is my accent natural?

Important:

It’s written as two words: je li, not jeli (which is usually a past tense form of to eat).

Could you also say Da li moj naglasak je prirodan or ako je moj naglasak prirodan here?

Not in the same way, and some are ungrammatical in this position.

je li vs da li
- In Croatian, je li is the standard form for yes/no questions.
- da li is very common in Serbian and in some spoken Croatian, but formal standard Croatian prefers je li.
- So you could hear Nisam sigurna da li je moj naglasak prirodan, but je li is stylistically better in standard Croatian.
ako
- ako means if in a conditional sense:
  - Ako je moj naglasak prirodan, onda… – If my accent is natural, then…
- It does not introduce an indirect yes/no question, so Nisam sigurna ako je moj naglasak prirodan is wrong or very odd.
Word order with da li / je li
- The natural order is je li moj naglasak prirodan (auxiliary + particle + subject + predicate).
- Da li moj naglasak je prirodan is wrong; the je should come before li: da li je moj naglasak prirodan.

Why is the word order je li moj naglasak prirodan and not je li prirodan moj naglasak?

Both are technically possible, but:

je li moj naglasak prirodan is the neutral, most natural order:
(aux) je li + subject + predicate adjective.
je li prirodan moj naglasak puts extra focus on prirodan (natural), almost like stressing “is it natural, my accent?” and can sound slightly marked or poetic.

In everyday speech and writing, you’ll nearly always hear je li moj naglasak prirodan.

Why is it moj naglasak prirodan and not prirodan naglasak?

You can say it both ways, but there is a nuance:

moj naglasak je prirodan
– normal, neutral statement: my accent is natural.
moj naglasak je prirodan naglasak
– my accent is a natural accent (sounds slightly redundant here).
prirodan naglasak as a phrase means a natural accent in general.

In this specific sentence, prirodan is used as a predicate adjective (after to be):
je (moj naglasak) prirodan, not as an attribute before the noun. That’s why it appears at the end.

Why is the adjective prirodan, not prirodna or prirodno?

Adjectives agree with the gender, number, and case of the noun:

naglasak (accent) is masculine singular in Croatian.
The nominative masculine singular form of the adjective is prirodan.

So:

moj naglasak (m.sg.) je prirodan (m.sg.)

If the noun were feminine, e.g. rečenica (sentence), you’d say:

Moja rečenica je prirodna. – My sentence is natural.

What is the function of ali here, and could you use something else like iako or ipak?

ali means but, introducing a contrast:

… je li moj naglasak prirodan, ali ljudi me razumiju.
= … whether my accent is natural, but people understand me.

Alternatives:

iako = although / even though
- Iako nisam sigurna je li moj naglasak prirodan, ljudi me razumiju.
  – Although I’m not sure whether my accent is natural, people understand me.
ipak = still / nevertheless (usually not a direct replacement for ali, more of a sentence adverb):
- Nisam sigurna je li moj naglasak prirodan, ali ljudi me ipak razumiju.
  – I’m not sure if my accent is natural, but people still / nevertheless understand me.

So ali is the straightforward coordinating conjunction, just like English but.

Why is it ljudi me razumiju and not ljudi razumiju me?

me is a clitic (an unstressed pronoun). Croatian clitics normally go to the second position in the clause (the so‑called Wackernagel position).

In ljudi me razumiju:

ljudi – first element
me – clitic in second position
razumiju – main verb

ljudi razumiju me is not grammatically impossible, but it sounds weird and marked in standard Croatian. You’d normally only move me for strong emphasis using the long form mene:

Ljudi razumiju mene. – It’s me that people understand (as opposed to someone else).

For a neutral sentence, always use ljudi me razumiju.

What’s the difference between me, mene, and mi?

All relate to I / me, but in different forms:

me
- short, unstressed accusative (direct object) pronoun
- used as a clitic in typical positions:
  - Ljudi me razumiju. – People understand me.
mene
- stressed accusative (and genitive) form
- used for emphasis or in certain prepositional phrases:
  - Ljudi razumiju mene, a ne njega.
    – People understand me, not him.
mi
- short, unstressed dative (to/for me) or genitive form, depending on context:
  - Ljudi mi pomažu. – People help me. (to me)
- It is not used as a direct object of razumjeti in this meaning.

So in ljudi me razumiju, me is correct because it’s a direct object.

Why is the verb razumiju and not something like razumem or razumeju?

This is standard Croatian conjugation in the present tense:

infinitive: razumjeti
oni/one/ona razumiju – they understand

In Serbian, the usual forms are:

infinitive: razumeti
oni/one/ona razumeju – they understand

So:

ljudi me razumiju – standard Croatian
ljudi me razumeju – standard Serbian

Both are correct in their own standards; the sentence you gave is in Croatian.

Could you rephrase the whole sentence in one or two other natural ways?

Yes, for example:

Nisam sigurna koliko je moj naglasak prirodan, ali ljudi me razumiju.
– I’m not sure how natural my accent is, but people understand me.
Nisam sigurna da mi je naglasak prirodan, ali me ljudi svejedno razumiju.
– I’m not sure that my accent is natural, but people still understand me.

All keep roughly the same meaning, with small nuances in emphasis.