O pogodnosti želim pregovarati.

It is built into the verb želim.

Croatian often drops subject pronouns because the verb ending already tells you the person and number.
Želim means I want.

So:

• želim = I want
• ti želiš = you want
• on/ona želi = he/she wants

You could add ja for emphasis, but it is not necessary:

• Ja želim pregovarati o pogodnosti.

Because Croatian word order is flexible.

Starting with o pogodnosti gives that part extra focus, almost like:

• As for the benefit, I want to negotiate.

A more neutral order would be:

• Želim pregovarati o pogodnosti.

Both are grammatical. The version with o pogodnosti first emphasizes the topic being negotiated.

O usually means about, regarding, or concerning, and it takes the locative case.

With pregovarati, a very common pattern is:

• pregovarati o nečemu = to negotiate about something
• pregovarati s nekim o nečemu = to negotiate with someone about something

So here:

• o pogodnosti = about the benefit / perk / favorable term

It is locative singular.

The basic noun is pogodnost. After the preposition o, it changes to the locative:

• pogodnost → o pogodnosti

That is why you do not see the dictionary form here.

Here it is singular.

This can confuse learners because -i sometimes looks plural. But after o, plural would be:

• o pogodnostima = about benefits / perks

So:

• o pogodnosti = about a/the benefit
• o pogodnostima = about benefits

Because it depends on želim.

In Croatian, after željeti (to want), you normally use an infinitive:

• želim pregovarati = I want to negotiate
• želim raditi = I want to work
• želim učiti = I want to study

This works much like English want to + verb.

Because pregovaram means I negotiate / I am negotiating, while pregovarati is the infinitive to negotiate.

Compare:

• Želim pregovarati. = I want to negotiate.
• Pregovaram. = I am negotiating / I negotiate.

So after želim, you need the infinitive, not another finite verb form.

Yes, pregovarati is imperfective.

That fits well because the sentence talks about wanting to engage in the process of negotiating, not necessarily about finishing it.

Croatian often uses the imperfective in this kind of context:

• Želim pregovarati = I want to negotiate

A perfective verb would suggest reaching a completed result. For example, a verb like ispregovarati can mean negotiating something successfully to a conclusion.

So pregovarati is the natural choice here.

Pogodnost is a broad word. Depending on context, it can mean:

• benefit
• perk
• advantage
• favorable condition
• convenience
• sometimes even a special offer or concession

So the exact English word depends on the situation. In business or negotiation contexts, it often means some kind of favorable term, benefit, or concession.

Because Croatian has no articles.

So pogodnosti could mean:

• a benefit
• the benefit

The exact meaning comes from context, not from an article.

This is very normal in Croatian. Learners often need to get used to relying on the situation rather than looking for a/the.

Yes, absolutely.

That is probably the most neutral and straightforward order for many contexts.

Compare:

• Želim pregovarati o pogodnosti. = neutral
• O pogodnosti želim pregovarati. = more emphasis on o pogodnosti

So the original sentence is fine, but it sounds a bit more marked or contrastive.

Sometimes, but not with exactly the same feel.

• pregovarati o nečemu = the standard way to say negotiate about/concerning something
• pregovarati oko nečega can sound more like negotiate over something, sometimes with a sense of wrangling or haggling

For a learner, pregovarati o + locative is the safest standard pattern to remember.