Ako ne dobijem godišnji u srpnju, ostat ću u gradu.

Yes. Godišnji is originally an adjective, but here it is being used as a noun-like word.

It is short for godišnji odmor, which means annual leave or vacation time from work. In everyday Croatian, people very often shorten it to just godišnji when the meaning is obvious.

So in this sentence, dobiti godišnji means to get annual leave / to be granted vacation time.

Grammatically, the omitted noun is understood, so godišnji functions as the direct object of dobijem.

After ako meaning if, Croatian usually does not use the future auxiliary in this kind of real future condition.

So Croatian says:

Ako ne dobijem ..., ostat ću ...

literally with a present-tense form in the if-clause, even though the meaning is future.

This is very normal Croatian grammar. English does something similar:

If I don’t get leave in July, I’ll stay in the city.

Notice that English also uses present in the if-clause, not if I won’t get.

This is about aspect, which is very important in Croatian.

• dobiti → perfective
• dobivati / dobivam → imperfective

Dobijem comes from dobiti, the perfective verb. It suggests a single completed result: whether I get the leave or not.

That fits the sentence, because the speaker is talking about one specific outcome.

If you used dobivam, it would sound more like a repeated or ongoing situation, which does not match this context well.

So Ako ne dobijem godišnji... is the natural choice.

In Croatian, ne is usually written separately from verbs.

So:

• dobijem → ne dobijem
• znam → ne znam
• idem → ne idem

There are some common exceptions, such as:

• nemam
• nisam
• neću

But with dobijem, the standard form is ne dobijem.

Because after u meaning in, Croatian uses the locative case when talking about location or time.

So:

• dictionary form: srpanj = July
• locative form: u srpnju = in July

Month names decline in Croatian, so they change form depending on the case.

With srpanj, the stem changes a little, which is why you get srpnju, not srpanju.

For the same reason: u meaning in takes the locative here.

So:

• grad = city / town
• u gradu = in the city / in town

This is a very common pattern:

• u školi = in school
• u kući = in the house
• u Zagrebu = in Zagreb

So u gradu is the correct locative form.

This is the Croatian future I tense.

It is made with:

• the infinitive of the verb
• plus the auxiliary ću

The verb is ostati = to stay / remain.

When ću comes after an infinitive ending in -ti, the final -i is dropped in writing:

• ostati + ću → ostat ću
• raditi + ću → radit ću
• pisati + ću → pisat ću

So ostat ću means I will stay.

Yes. That is also correct.

Both are natural:

• Ostat ću u gradu.
• Ja ću ostati u gradu.

The difference is mostly about word order and emphasis.

• Ostat ću u gradu is compact and neutral.
• Ja ću ostati u gradu puts a bit more emphasis on I or uses a fuller word order.

Croatian word order is flexible, but the little auxiliary ću cannot normally stand completely on its own at the beginning of a clause. That is why ću ostati by itself is not the usual way to start a sentence.

Yes. Croatian allows several word orders, for example:

• Ako ne dobijem godišnji u srpnju, ostat ću u gradu.
• Ostat ću u gradu ako ne dobijem godišnji u srpnju.

The basic meaning stays the same.

The version with Ako... first is very natural because it introduces the condition before the result. The second version may sound a little more focused on the result ostat ću u gradu.

Yes, in standard writing it should be there.

The first part, Ako ne dobijem godišnji u srpnju, is a subordinate clause introduced by ako. When that clause comes first, it is normally followed by a comma before the main clause:

Ako ne dobijem godišnji u srpnju, ostat ću u gradu.

If the main clause comes first, the comma is usually not needed:

Ostat ću u gradu ako ne dobijem godišnji u srpnju.

In Croatian, names of months are normally written with a lowercase letter.

So Croatian writes:

• siječanj
• veljača
• srpanj
• prosinac

This is different from English, where January, July, and so on are capitalized.

So u srpnju with a lowercase s is correct Croatian spelling.