Ovo radno mjesto je dostupno.

Because mjesto is a neuter singular noun, and ovo has to agree with it.

Croatian demonstratives change form depending on gender, number, and case.

Here the noun is:

• mjesto = a neuter noun
• singular
• in the nominative case

So the correct form is:

• masculine: ovaj
• feminine: ova
• neuter: ovo

That is why the sentence starts with ovo radno mjesto.

They both agree with the noun mjesto, which is neuter singular.

In Croatian, adjectives usually match the noun they describe in:

• gender
• number
• case

So:

• radno mjesto = work place / job position
• dostupno = available

Because mjesto is neuter singular, the adjectives take the neuter singular form:

• radan / radna / radno
• dostupan / dostupna / dostupno

So the -o ending is a sign of neuter singular agreement.

Radno mjesto is a very common expression meaning job position, post, or sometimes workplace, depending on context.

Literally:

• radno = work-related / working
• mjesto = place

So word-for-word it looks like work place, but in real usage it often means:

• a job opening
• a position in a company
• a post

So in many contexts, ovo radno mjesto is best understood as this position rather than a physical place.

Je is the 3rd person singular present tense of biti (to be).

So:

• ja sam = I am
• ti si = you are
• on/ona/ono je = he/she/it is

In this sentence:

• Ovo radno mjesto je dostupno.
• This job position is available.

So je simply means is.

Usually, in normal full sentences, no—you normally keep it.

Croatian is not like Russian, where the present-tense to be is usually omitted. In Croatian, je is normally expressed:

• Ovo radno mjesto je dostupno.

However, in some special styles such as:

• headlines
• advertisements
• notes
• very compressed style

you might sometimes see the verb omitted for brevity. But for standard sentence-building, learners should use je.

It can be correct, but it depends on the exact nuance.

Dostupan/dostupno often means:

• available
• accessible
• obtainable

So radno mjesto je dostupno can mean the position is available.

But in job-related contexts, Croatian very often uses:

• slobodno radno mjesto = vacant position / open position
• radno mjesto je slobodno = the position is vacant

So if you are talking specifically about a job opening, slobodno may sound more idiomatic in many contexts.
If you are emphasizing that something is available to applicants or accessible, dostupno also works.

Yes, Croatian word order is more flexible than English word order.

The neutral order here is:

• Ovo radno mjesto je dostupno.

But Croatian can change word order for emphasis or style, for example:

• Radno mjesto je dostupno. = The position is available.
• Dostupno je ovo radno mjesto. = This position is available.
  This sounds more marked and would usually emphasize dostupno.

Even though word order can move, the forms still show the grammatical relationships. For learners, the given order is the safest and most neutral one.

It is in the nominative singular.

Why nominative?

Because it is the subject of the sentence:

• Ovo radno mjesto = the thing being talked about
• je dostupno = is available

The nominative is the normal case for the subject of a sentence.

You can also tell from the agreement:

• ovo = nominative neuter singular
• radno = nominative neuter singular
• mjesto = nominative neuter singular
• dostupno = nominative neuter singular predicate adjective agreeing with the subject

Yes, mjesto is a neuter noun.

A useful clue is that many Croatian nouns ending in -o or -e are neuter, though not every single one follows the same pattern in all details.

So you get forms like:

• ovo mjesto = this place
• to mjesto = that place
• lijepo mjesto = a beautiful place

Because mjesto is neuter, words agreeing with it must also use neuter forms.

The agreeing words would change to match the new noun.

For example, with a feminine noun:

• Ova pozicija je dostupna.
• This position is available.

With a masculine noun:

• Ovaj posao je dostupan.
• This job is available.

Compare the agreement:

• neuter: ovo ... dostupno
• feminine: ova ... dostupna
• masculine: ovaj ... dostupan

This is a very important Croatian pattern.

A rough English-friendly pronunciation is:

• OH-voh RAHD-noh MYEH-stoh yeh doh-STOOP-noh

A few notes:

• j in Croatian is like English y in yes
• mj in mjesto is pronounced together, roughly like mye
• o is a clear short vowel, not a diphthong like in many English accents
• Croatian spelling is quite phonetic, so words are usually pronounced close to how they are written

So:

• je sounds like ye
• mjesto sounds roughly like MYEH-stoh

Yes. Ovo can be used both:

1. with a noun

   • ovo radno mjesto = this job position

2. on its own

   • Ovo je dobro. = This is good.
   • Što je ovo? = What is this?

In your sentence, ovo is directly modifying radno mjesto, so it means this before a noun.

It is singular here.

Singular:

• ovo radno mjesto je dostupno = this job position is available

Plural:

• ova radna mjesta su dostupna = these job positions are available

Notice how several words change:

• ovo → ova
• radno mjesto → radna mjesta
• je → su
• dostupno → dostupna

That is because Croatian marks number throughout the sentence.