Het teambelang bepaalt de proefperiode.

Because teambelang is a het-word in Dutch, so it takes the definite article het.

A useful thing to know is that compounds usually keep the grammatical gender of the main word, which is often the last part. Here, the main word is belang. Since het belang is correct, the compound becomes het teambelang.

So:

• het belang = the interest
• het teambelang = the team interest / the interest of the team

Dutch forms compound nouns much more readily than English does. Where English might use two words or a phrase, Dutch often combines them into a single word.

So:

• team + belang → teambelang
• proef + periode → proefperiode

This is very normal in Dutch. English learners often expect something like team belang, but standard Dutch writes it as teambelang.

It is a compound noun made up of:

• team = team
• belang = interest, benefit, concern

Together, teambelang means something like the interest of the team or what is best for the team.

In Dutch compounds, the last part is usually the core noun, and the first part modifies it. So this is literally a kind of belang.

Because the subject is singular: het teambelang.

The infinitive is bepalen. In the present tense, with a singular third-person subject, Dutch usually adds -t:

• ik bepaal
• jij bepaalt
• hij/zij/het bepaalt

Since het teambelang is treated like it, the correct form is bepaalt.

The subject is het teambelang.

You can tell because it is the thing doing the action of the verb bepaalt. In other words, the team’s interest is what determines something.

The structure is:

• Het teambelang = subject
• bepaalt = verb
• de proefperiode = object

So it follows a straightforward Dutch main-clause word order: subject + verb + object.

Because proefperiode is a de-word.

Again, the last part of the compound usually determines the gender. The core noun here is periode, and de periode is correct in Dutch. So the full compound is also de proefperiode.

Compare:

• de periode
• de proefperiode

Yes. It consists of:

• proef = trial, test
• periode = period

So proefperiode means trial period or probation period, depending on the context.

Like teambelang, it is written as one word because Dutch normally joins nouns into compounds.

Dutch can sometimes use a van phrase, but compounds are often more natural and more concise.

So Dutch prefers:

• het teambelang

rather than a longer phrase like:

• het belang van het team

Both can be understandable, but the compound is very common and compact. Dutch often packs this kind of relationship into a single noun.

Yes. In a normal main clause, Dutch often has the finite verb in the second position.

The sentence you have is the basic order:

• Het teambelang bepaalt de proefperiode.

But another element could come first, and then the verb would still stay second:

• De proefperiode bepaalt het teambelang.
  This changes the meaning.
• Vandaag bepaalt het teambelang de proefperiode.
  Here vandaag comes first, and bepaalt still stays in second position.

So Dutch word order is flexible, but the finite verb in a main clause is usually in position two.

Roughly, it sounds like:

• team with a long vowel like English taym
• belang with stress usually on the second part of the compound: be-LANG

A rough English-friendly guide could be:

• taym-buh-LAHNG

And proefperiode is roughly:

• proof-puh-ree-OH-duh

Exact pronunciation varies a bit by speaker, but the important thing for learners is that Dutch compounds are usually pronounced smoothly as one unit.

Not necessarily. The sentence is grammatically natural, but in real contexts speakers might choose a slightly more specific or idiomatic phrasing depending on what they mean.

For example, they might also say:

• Het belang van het team bepaalt de proefperiode.
• De proefperiode wordt bepaald door het teambelang.

But your original sentence is perfectly good Dutch and is useful because it clearly shows:

• a het-word compound: het teambelang
• a present-tense verb: bepaalt
• a de-word compound: de proefperiode