Da sam ranije znala za kašnjenje, ne bih ni ulazila u čekaonicu.

In this sentence, da introduces an unreal, counterfactual condition: Da sam ranije znala... = If I had known earlier...

Croatian commonly uses:

• da for unreal or contrary-to-fact conditions
• ako for real, open, or likely conditions

So here da tells you the speaker did not know earlier in reality.

Because Croatian normally builds this type of past unreal conditional as:

• da + perfect in the condition clause
• conditional in the result clause

So:

• Da sam znala = If I had known
• ne bih... = I would not have...

English uses had known / would have entered, but Croatian does not copy that structure exactly. The standard Croatian pattern is exactly what you see here.

Those are l-participles, and they agree with the speaker’s gender.

Here, znala and ulazila show that the speaker is female.

If the speaker were male, you would get:

• Da sam ranije znao za kašnjenje, ne bih ni ulazio u čekaonicu.

So this is not a tense change; it is gender agreement.

Because Croatian often drops subject pronouns when they are already clear from the verb forms.

Here, sam and bih already show first person singular (I), so ja is unnecessary.

You could say Da sam ja ranije znala..., but that would sound more emphatic, like If I had known earlier...

Ranije means earlier or sooner.

It tells you when the speaker would have known: not at the actual moment, but before that.

It modifies znala:

• Da sam ranije znala... = If I had known earlier...

Its position is somewhat flexible. For example:

• Da sam ranije znala...
• Da sam znala ranije...

Both are possible, though the version in your sentence is very natural.

Because znati za + accusative is a fixed expression meaning to know about, to be aware of.

So:

• znati za kašnjenje = to know about the delay

Without za, znati usually works differently, for example:

• Znam odgovor. = I know the answer.
• Znam da kasni. = I know that he/she is late.

Here the idea is not knowing the delay itself, but being aware of the delay, so za is the natural choice.

It actually is in the correct case: accusative.

The preposition za in znati za takes the accusative case. But kašnjenje is a neuter singular noun, and for many neuter nouns the nominative and accusative forms look the same.

So:

• nominative: kašnjenje
• accusative: kašnjenje

The case changed grammatically, but the form stayed the same.

Here ni means even, in the sense of not even.

So:

• ne bih ni ulazila = I wouldn’t even be entering / I wouldn’t even go in

In negative sentences, Croatian often uses ni to add that extra emphasis.

It can also shift depending on what you want to emphasize. For example:

• Ne bih ni ulazila u čekaonicu. = I wouldn’t even enter the waiting room.
• Ne bih ulazila ni u čekaonicu. = I wouldn’t enter even the waiting room.

The meaning is similar, but the focus moves slightly.

This is a question of aspect.

• ulaziti = imperfective
• ući = perfective

So:

• ne bih ni ulazila presents the action as something the speaker would not even have started / bothered doing
• ne bih ni ušla would focus more on the completed act of entering

Both can be possible, but they are not identical in nuance.

The form in your sentence sounds like: I wouldn’t even have been going in / I wouldn’t even have bothered entering.
It makes the action feel more like something the speaker would have avoided altogether.

Because Croatian uses different cases after u depending on whether you mean movement or location.

• u + accusative = into, movement toward a place
• u + locative = in, location inside a place

Here the verb is about entering, so motion is involved:

• u čekaonicu = into the waiting room

Compare:

• Ulazim u čekaonicu. = I am going into the waiting room.
• Sjedim u čekaonici. = I am sitting in the waiting room.

Because sam and bih are clitics in Croatian. Clitics are short unstressed words that usually stand near the beginning of the clause.

So you get:

• Da sam ranije znala...
• ne bih ni ulazila...

That placement is normal Croatian word order.

Also, ne bih behaves as a fixed unit in standard usage, so you do not split it up.

Yes, Croatian word order is fairly flexible, but not completely free.

For example, these are possible:

• Da sam ranije znala za kašnjenje, ne bih ni ulazila u čekaonicu.
• Da sam za kašnjenje ranije znala, ne bih ni ulazila u čekaonicu.
• Da sam znala ranije za kašnjenje, ne bih ni ulazila u čekaonicu.

But the original version sounds the most natural and neutral.

What usually stays fixed is the placement of clitics like sam and bih, which still have to follow Croatian clitic rules.