Imam kupon za popust, ali vrijedi samo ako kupim dva ista pakiranja.

Imam means I have. It is the 1st person singular present form of imati (to have).

A few present-tense forms are:

• ja imam = I have
• ti imaš = you have
• on/ona/ono ima = he/she/it has
• mi imamo = we have
• vi imate = you have
• oni/one/ona imaju = they have

In Croatian, the subject pronoun ja is often left out because the verb ending already shows who is doing the action.

Kupon za popust literally means coupon for a discount.

• kupon = coupon
• za = for
• popust = discount

So Croatian uses za in a very natural way here: a coupon for a discount.

This is similar to many other expressions:

• karta za koncert = a ticket for the concert
• novac za hranu = money for food
• lijek za glavobolju = medicine for a headache

After za, Croatian often uses the accusative case.
The noun popust is a masculine inanimate noun, and in the accusative singular it looks the same as the nominative singular:

• nominative: popust
• accusative: popust

So za popust is correct.

If the noun changed in the accusative, you would see a different form, but here the form stays the same.

Ali means but.

It connects two ideas:

• Imam kupon za popust = I have a discount coupon
• ali vrijedi samo... = but it is valid only...

It usually appears between two clauses, much like but in English.

Examples:

• Htio sam doći, ali nisam mogao. = I wanted to come, but I couldn’t.
• Skupo je, ali dobro. = It’s expensive, but good.

Here vrijedi means is valid, counts, or applies.

The verb is vrijediti. Its meaning depends on context:

• To vrijedi puno. = That is worth a lot.
• Ponuda vrijedi do petka. = The offer is valid until Friday.
• Kupon vrijedi samo uz račun. = The coupon is valid only with a receipt.

So in your sentence, vrijedi does not mean is worth in a money sense. It means the coupon can only be used / applies only under a certain condition.

Yes. Samo ako means only if.

• samo = only
• ako = if

So:

• vrijedi samo ako... = it is valid only if...

This is a very common structure in Croatian.

Examples:

• Dođi samo ako možeš. = Come only if you can.
• Popust vrijedi samo ako platite gotovinom. = The discount is valid only if you pay in cash.

This is one of the most common learner questions, because it involves aspect.

• kupiti = to buy (perfective)
• kupovati / kupujem = to be buying / to buy habitually (imperfective)

Here ako kupim means if I buy in the sense of if I end up making that purchase as a complete event. Croatian often uses the perfective present after ako when talking about a future condition.

So:

• ako kupim = if I buy / if I do buy
• ako kupujem would sound more like if I am buying or if I buy regularly, which does not fit as well here

Compare:

• Ako kupim dva ista pakiranja, kupon vrijedi. = If I buy two identical packs, the coupon is valid.
• Kad kupujem, uvijek gledam cijene. = When I’m shopping / when I buy, I always look at prices.

Yes, kupim is formally a present-tense form, but because it comes from a perfective verb (kupiti), it often refers to a future completed action, especially in clauses with words like ako (if) or kad (when, in some contexts).

So Croatian often does this:

• Ako dođem, nazvat ću te. = If I come, I’ll call you.
• Ako kupim dva ista pakiranja, kupon vrijedi. = If I buy two identical packs, the coupon is valid.

This is normal Croatian grammar, even though English uses a present form too in if I buy.

Because after dva (two), the noun usually appears in a special form that looks like the genitive singular for many neuter nouns.

The noun is:

• pakiranje = package / pack

After dva, it becomes:

• dva pakiranja = two packages / two packs

So:

• jedno pakiranje = one pack
• dva pakiranja = two packs
• tri pakiranja = three packs
• pet pakiranja = five packs

For neuter nouns like this, the form after 2, 3, 4 is often the same as after 5+, at least on the noun itself.

Ista means same / identical here, and it agrees with pakiranja.

The basic adjective is isti = same.
It changes its form to match the noun’s gender, number, and case.

Because pakiranja is a neuter plural-type quantity expression after dva, the adjective appears as ista:

• isto pakiranje = the same pack
• dva ista pakiranja = two identical packs

So ista is the correct agreeing form in this phrase.

In natural English, the best translation is two identical packages/packs or two of the same pack.

Croatian isti often covers what English expresses as:

• same
• identical
• matching
• the same kind of

In a shopping context, dva ista pakiranja usually means two packs of the same product/size/type, not just any two packages.

It depends on context.

Pakiranje can mean:

• pack
• package
• packaging

In this sentence, the most natural meaning is pack or package, especially in a store or supermarket context.

For example:

• dva ista pakiranja kave = two identical packs of coffee
• veliko pakiranje = a large pack
• obiteljsko pakiranje = a family pack

So here pack is probably the best English choice.

Yes. Croatian often leaves out subjects when they are clear from context.

In English, you need it:

• it is valid only if...

In Croatian, the subject is understood from the previous noun phrase:

• Imam kupon za popust, ali vrijedi samo ako...

The implied subject is kupon (the coupon). Croatian does not need to repeat it.

You could say:

• Imam kupon za popust, ali kupon vrijedi samo ako kupim dva ista pakiranja.

But that sounds repetitive, so native speakers usually omit kupon.

The given word order is natural, but Croatian word order is fairly flexible.

Standard and natural:

• Imam kupon za popust, ali vrijedi samo ako kupim dva ista pakiranja.

Possible variations for emphasis include:

• Imam kupon za popust, ali samo vrijedi ako kupim dva ista pakiranja.
• Kupon za popust imam, ali vrijedi samo ako kupim dva ista pakiranja.

However, the original version is the most neutral and idiomatic.

In Croatian, word order often changes to highlight information, but not every possible rearrangement sounds equally natural.

Yes, a native speaker could absolutely say this. It sounds natural.

A few everyday alternatives might be:

• Imam kupon za popust, ali vrijedi samo ako uzmem dva ista pakiranja.
• Imam kupon, ali vrijedi samo ako kupim dva ista pakiranja.
• Kupon vrijedi samo ako kupim dva ista pakiranja.

Using uzmem instead of kupim can sound a bit more colloquial in some shopping situations, but kupim is perfectly normal and clear.