Danas svi dolaze na sastanak osim njega.

A word-by-word breakdown:

• Danas = today
• svi = everyone / all
• dolaze = are coming / come
• na = to / onto, but here it means to in the sense of going to an event
• sastanak = meeting
• osim = except
• njega = him

So the full sentence means: Today everyone is coming to the meeting except him.

Because the subject is svi, which means everyone / all people, and that is grammatically plural in Croatian.

• svi dolaze = everyone is coming / all are coming

Even though English often uses singular-looking everyone, Croatian uses the plural idea here.

Svi is the masculine plural form meaning all or everyone when referring to a group of people in a general way.

Compare:

• svi = all people / everyone
• sve = all things / everything or feminine/neuter forms in some contexts
• svatko = everyone / each person

So:

• Svi dolaze. = Everyone is coming.
• Sve dolazi. would not fit here for people.
• Svatko dolazi. is possible, but it sounds more like each person is coming.

In this sentence, svi is the most natural choice.

In Croatian, some nouns take na, and others take u, depending on usage, not just literal logic.

With sastanak (meeting), Croatian normally says:

• ići na sastanak = to go to a meeting
• doći na sastanak = to come to a meeting

So na sastanak is the standard expression.

Even though English says in a meeting in some contexts, when talking about attending it, Croatian uses na sastanak.

Sastanak is in the accusative singular.

The preposition na often takes the accusative when it shows movement toward something:

• na sastanak = to the meeting

Since sastanak is a masculine noun that refers to something non-living, its accusative singular looks the same as the nominative singular:

• nominative: sastanak
• accusative: sastanak

So the form does not change, even though the case does.

Because the preposition osim requires the genitive case.

The pronoun on means he, but after osim you need the genitive form:

• nominative: on
• genitive: njega

So:

• osim njega = except him

This is one of the most important things to notice in the sentence.

Usually in this sentence it means except him.

• Danas svi dolaze na sastanak osim njega.
  = Today everyone is coming to the meeting except him.

In some contexts, osim can also be understood more like besides or apart from, but here the natural meaning is clearly that he is the one person not coming.

After a preposition like osim, Croatian uses the full stressed pronoun form, not the short clitic form.

So:

• njega = full form
• ga = short unstressed form

You can say:

• Vidim ga. = I see him.

But after osim, you need:

• osim njega = except him

Not osim ga.

Yes, dolaze is present tense.

In Croatian, the present tense is often used for:

• actions happening now
• scheduled future events
• general statements

So Danas svi dolaze na sastanak can mean:

• Today everyone is coming to the meeting
• Today everyone comes to the meeting

In natural English, is coming sounds best here.

The dictionary form is dolaziti, which is an imperfective verb meaning to come / to be coming / to arrive repeatedly or generally.

Here are some forms:

• dolaziti = infinitive
• dolazim = I come / I am coming
• dolaziš = you come / are coming
• dolaze = they come / are coming

Since svi is plural, we use dolaze.

Yes, Croatian word order is flexible, and danas is placed first here for a natural time-topic order.

This sentence sounds very normal:

• Danas svi dolaze na sastanak osim njega.

But other orders are possible, for example:

• Svi danas dolaze na sastanak osim njega.
• Na sastanak danas svi dolaze osim njega.

The meaning stays mostly the same, but the emphasis changes.

Putting danas first answers the time question right away: today.

Yes, but in natural English, everyone is usually better in this sentence.

So:

• svi = all / everyone

Natural translation:

• Today everyone is coming to the meeting except him.

A more literal translation could be:

• Today all are coming to the meeting except him.

That is understandable, but less natural in English.

Yes, it is completely natural and idiomatic.

It is a normal everyday sentence, and it shows several very useful patterns:

• time expression first: Danas
• plural subject: svi
• present tense verb: dolaze
• motion/event phrase with na
  • accusative: na sastanak
• exception phrase with osim
  • genitive: osim njega

So it is a very good example sentence for learners.