Pazi da ne prospeš juhu na stolnjak.

Pazi is the 2nd person singular imperative of paziti.

In this sentence, it means something like:

• Be careful
• Watch out
• Take care

So Pazi da ne... is a very common Croatian pattern meaning Be careful not to...

Croatian often uses da + present-tense verb where English uses an infinitive.

So:

• Pazi da ne prospeš juhu
  literally: Be careful that you do not spill the soup
• natural English: Be careful not to spill the soup

This is completely normal Croatian structure. After verbs like paziti, gledati, htjeti, trebati (in some uses), Croatian very often prefers a da-clause instead of an infinitive.

Prospeš is the 2nd person singular present form of the verb prosuti / prosipati in the sense to spill.

Here it matches the implied subject you:

• (ti) prospeš = you spill

Because the main verb pazi is an imperative addressed to one person, the subordinate verb also stays in the 2nd person singular.

So the sentence is speaking directly to one person:

• Pazi da ne prospeš... = Be careful not to spill...

That is normal in Croatian after da.

Even when English would express a future or potential action, Croatian often uses the present form after da:

• Pazi da ne zakasniš = Be careful not to be late
• Pazi da ne padneš = Be careful not to fall
• Pazi da ne prospeš juhu = Be careful not to spill the soup

So this is not really about present time in the English sense. It is just the standard Croatian form in this structure.

Ne is the normal Croatian negation word for verbs.

So:

• prospeš = you spill
• ne prospeš = you do not spill

In this sentence, the negative is needed because the meaning is:

• Be careful not to spill the soup

Croatian places ne directly before the verb in ordinary negation.

Because juhu is the accusative singular form of juha.

The verb prosuti / prosipati takes a direct object, and direct objects are usually in the accusative:

• nominative: juha = soup
• accusative: juhu = soup as the thing being spilled

So:

• prospeš juhu = you spill the soup

This is a very common pattern in Croatian:

• jesti juhu = to eat soup
• kuhati juhu = to cook soup
• prospeti juhu = to spill soup

Because na can take different cases depending on meaning.

Here is the key difference:

• na + accusative = movement onto something / result reaching a surface
• na + locative = location on something

In this sentence, the soup would end up onto the tablecloth, so Croatian uses accusative:

• na stolnjak = onto the tablecloth

Compare:

• Juha je na stolnjaku. = The soup is on the tablecloth.
  Here it is location, so locative: na stolnjaku

So the sentence uses na stolnjak because it expresses the result of spilling.

Yes, very close to that.

In natural English, we usually just say:

• spill the soup on the tablecloth

But Croatian often marks the direction/result more clearly with na + accusative, which is closer to:

• spill the soup onto the tablecloth

So the Croatian grammar is slightly more explicit than the most natural English translation.

Because Croatian normally leaves out subject pronouns when they are already clear from the verb form.

The forms themselves show the person:

• pazi = you (singular, imperative)
• prospeš = you (singular)

So ti is unnecessary here.

You could include ti for emphasis, but normally you would not:

• Pazi da ti ne prospeš juhu... would sound odd or overly emphatic in most contexts

Croatian is a pro-drop language, so omitted subject pronouns are very normal.

Yes, very common.

It is one of the most useful everyday warning patterns in Croatian:

• Pazi da ne padneš. = Be careful not to fall.
• Pazi da ne zakasniš. = Be careful not to be late.
• Pazi da ne zaboraviš ključ. = Be careful not to forget the key.
• Pazi da ne prospeš juhu na stolnjak. = Be careful not to spill the soup on the tablecloth.

So this sentence is very natural and idiomatic.

Here the verb is effectively perfective in meaning: prosuti means to spill once / to cause the spilling to happen, as a complete event.

That fits the sentence well, because the speaker is warning against one whole event happening:

• don’t spill it

Croatian often uses a perfective verb in warnings about a single undesirable event:

• Pazi da ne padneš. = Be careful not to fall.
• Pazi da ne razbiješ čašu. = Be careful not to break the glass.
• Pazi da ne prospeš juhu. = Be careful not to spill the soup.

If you used an imperfective verb, the nuance could shift toward an ongoing or repeated action, which is less natural here.

Yes, many speakers would say that too, and it sounds natural.

Both prospeti/prosuti and proliti can be used for spill, depending on region, style, and the exact image of the action.

Very roughly:

• proliti is often very common for spilling liquid
• prosuti / prospeti is also common, especially for spilling something out

Since juha is liquid, proliješ juhu is also perfectly understandable and natural.

So this is more about vocabulary choice than grammar.

The dictionary form is stolnjak, meaning tablecloth.

In this sentence, the form happens to look the same as the dictionary form because it is masculine singular accusative, and for many masculine inanimate nouns, accusative singular = nominative singular.

So:

• nominative: stolnjak
• accusative: stolnjak

That is why it does not visibly change, unlike juha → juhu.

Yes. Croatian word order is fairly flexible, although the given version is very natural:

• Pazi da ne prospeš juhu na stolnjak.

You might also hear:

• Pazi da juhu ne prospeš na stolnjak.
• Pazi da ne prospeš na stolnjak juhu.

But these alternatives usually add emphasis or sound more marked. For a neutral sentence, the original order is the best choice.

So for learners, the safest version is:

• Pazi da ne prospeš juhu na stolnjak.