Learn Hardcore Croatian: Sve rečenice na početku nemaju smisla, ali nakon nekoliko dana vježbe postaje lakše. - All the sentences at the beginning do not make sense, but after a few days of practice it becomes easier.

In this sentence, Sve rečenice na početku nemaju smisla is naturally translated as All the sentences don’t make sense at first (or Every sentence doesn’t make sense at first), but there is no separate word for the in Croatian.

Why is the word order Sve rečenice na početku nemaju smisla and not Na početku sve rečenice nemaju smisla? Is one of them wrong?

Both are correct; the difference is only in emphasis.

Sve rečenice na početku nemaju smisla
– Neutral focus on all the sentences.
– Roughly: All the sentences, at the beginning, don’t make sense.
Na početku sve rečenice nemaju smisla
– Slightly more emphasis on at the beginning.
– Roughly: At the beginning, all the sentences don’t make sense.

Croatian word order is relatively flexible. You usually put at the front what you want to highlight. Here, both orders sound natural in everyday speech.

What is the difference between na početku and u početku? Could I use u početku here?

Both exist, but they’re used a bit differently:

na početku = at the beginning (of something concrete)
- na početku tečaja – at the beginning of the course
- na početku knjige – at the beginning of the book
u početku = initially, at first, in the beginning (more abstract / general)
- U početku je bilo teško. – It was difficult at first.

In your sentence, Sve rečenice na početku nemaju smisla, we’re talking about the beginning phase of practice/learning, so na početku is very natural: at the start (of learning / of the course).

You could say U početku sve rečenice nemaju smisla, and it would still be understandable, but na početku is more idiomatic here because we imagine a concrete beginning of the learning process.

Why is it nemaju smisla and not something like nemaju smisao?

The phrase imati smisla is a fixed expression meaning to make sense.

ima smisla – it makes sense
nema smisla – it doesn’t make sense

Grammatically, smisla is the genitive singular of smisao. In this idiom, Croatian uses the genitive, not the accusative:

imati + genitive: imati smisla – literally: to have (some) sense

So:

rečenice imaju smisla – the sentences make sense
rečenice nemaju smisla – the sentences don’t make sense

Using smisao here (nemaju smisao) would sound wrong; native speakers don’t say it that way in this meaning.

Why is it nemaju, not ne imaju? Can I separate ne and imaju?

You cannot separate them here. In Croatian, the negative particle ne usually attaches directly to the present-tense form of the verb and becomes one word:

ne + imaju → nemaju
ne + ide → ne ide (here it stays separate)
ne + znam → ne znam (also separate)
ne + mogu → ne mogu (separate)

With imati specifically, it is normally written as one word in the present tense negative:

imam → nemam
ima → nema
imamo → nemamo
imate → nemate
imaju → nemaju

So Sve rečenice na početku nemaju smisla is correct; ne imaju would look wrong.

In nakon nekoliko dana vježbe, why are dana and vježbe in that form? What case is this?

Both dana and vježbe are in the genitive case.

nakon always requires the genitive:
- nakon posla – after work
- nakon ručka – after lunch
- nakon nekoliko dana – after a few days
nekoliko (a few, several) also takes genitive plural:
- nekoliko dana – a few days
- nekoliko ljudi – several people
vježba → vježbe is genitive singular:
- bez vježbe – without practice
- dosta vježbe – a lot of practice
- nekoliko dana vježbe – a few days of practice

So nakon nekoliko dana vježbe = after a few days of practice, and genitive is triggered both by nakon and by the quantifier nekoliko.

Could I say nakon nekoliko dana vježbanja instead of vježbe? Is there a difference?

Yes, you can say nakon nekoliko dana vježbanja, and it is also correct and natural.

vježba (noun) – practice (as a thing, an exercise)
vježbanje (verbal noun) – the act of practising

Nuance:

nekoliko dana vježbe – a few days of (regular) practice
nekoliko dana vježbanja – a few days of practising (focus a bit more on the activity itself)

In everyday language, they’re very close in meaning here. Both sound fine.

What is the subject of postaje lakše? Why is there no noun and why is lakše in this form?

This is an impersonal construction. There is no explicit subject in Croatian; it’s understood from context.

postaje lakše ≈ it becomes easier.

postaje – 3rd person singular of postati (to become)
lakše – neuter comparative form of lako (easy)

Why neuter? Because when Croatian uses an impersonal it (like English it is cold, it is easy), adjectives or their comparative forms often appear in neuter singular:

Teško je. – It is hard.
Bit će lakše. – It will be easier.
Postaje zanimljivo. – It is becoming interesting.

So here, postaje lakše literally means something like it is becoming easier, where it refers to the whole learning process / working with sentences, understood from context.

What is the difference between lakše and lakši? Why is it lakše here?

Both come from lak / lagan (easy), but:

lakši – comparative adjective, masculine singular
- lakša knjiga – an easier book (feminine)
- lakši zadatak – an easier task (masculine)
lakše – comparative adverb or neuter form, often used impersonally
- Učiti je lakše. – Learning is easier.
- Postaje lakše. – It’s becoming easier.

In postaje lakše, we’re not comparing a specific noun like a task or a book. We’re describing the general situation (learning / doing exercises). In that abstract, impersonal sense, Croatian prefers lakše, not lakši.

If you had a clear neuter noun, you could also match it:

Učenje postaje lakše. – The learning becomes easier.

But you would not say postaje lakši here without a matching masculine noun.

Could I drop vježbe and just say ali nakon nekoliko dana postaje lakše?

Yes, you can.

ali nakon nekoliko dana postaje lakše = but after a few days it becomes easier.

By dropping vježbe, you remove the explicit mention of practice, but it is still understood from the context (we are already talking about learning / exercises).

With vježbe: after a few days of practice it becomes easier (more concrete).
Without vježbe: after a few days it becomes easier (slightly more general, but still clear).

Both are natural; including vježbe just makes the cause of improvement more explicit.

Why is there a comma before ali? Is it always used like that?

Yes, in standard Croatian, you normally put a comma before ali when it connects two clauses:

Rečenice su teške, ali nakon nekoliko dana postaje lakše.
Pokušao sam, ali nisam uspio.

ali is a coordinating conjunction meaning but, and Croatian punctuation rules require a comma before such conjunctions when they connect whole clauses.

So ..., ali ... with a comma is the standard written form.