De deur is open, maar ik sluit haar straks.

In this sentence, open is an adjective, not a past participle.

• De deur is open = The door is open
• It describes the state of the door.

Compare:

• De deur is open = the door is in an open state
• De deur is geopend = the door has been opened / the door is opened

So open is the normal, natural choice when you want to describe the condition of the door.

This is a very common question.

In Dutch, some nouns can be referred to with grammatical gender, not natural gender. De deur is traditionally a feminine noun, so you may see haar used to refer back to it.

So:

• de deur → haar

However, this can sound formal, literary, or regional to many learners, especially in modern Dutch from the Netherlands. In everyday speech, people often avoid this kind of pronoun for objects.

A speaker might instead say:

• De deur is open, maar ik sluit de deur straks.
• De deur is open, maar ik doe hem straks dicht.

So haar is grammatically explainable, but not always the most neutral everyday choice for modern spoken Dutch.

Yes, sluit is the present tense of sluiten.

• ik sluit = I close / I am closing

Dutch often uses the present tense for the future when a time word makes the meaning clear. Here, straks shows that the action will happen later.

So:

• ik sluit haar straks = I’ll close it later

This is very normal Dutch. You do not need zal here.

Compare:

• Ik sluit haar straks. = I’ll close it later.
• Ik zal haar straks sluiten. = I will close it later.

Both are possible, but the first is often more natural.

Straks usually means later, often later today or in a little while. The exact timing depends on context.

Examples:

• Ik doe het straks. = I’ll do it later.
• Tot straks! = See you in a bit! / See you later!

So in this sentence:

• maar ik sluit haar straks = but I’ll close it later

It does not necessarily mean immediately. It just means not now, but later.

Because this is a main clause.

Dutch main clauses normally follow the verb-second rule:

• first position: maar does not count as the first clause element in the same way a normal constituent does here; after maar, the clause itself begins
• then the finite verb comes early: ik sluit
• then the object and other information: haar straks

So the structure is:

• maar
  • ik
    • sluit
      • haar
        • straks

You would expect ... haar straks sluit in a subordinate clause, for example:

• ..., omdat ik haar straks sluit.
• ..., omdat = because
• In subordinate clauses, the verb goes toward the end.

Both can work, but they are a bit different in tone.

• sluiten = to close
• dichtdoen = to shut / to close

For a door, both are common:

• Ik sluit de deur.
• Ik doe de deur dicht.

Sluiten can sound a little more formal or neat. Dichtdoen is very common in everyday speech.

So this sentence could also be:

• De deur is open, maar ik doe hem straks dicht.

That version may sound more conversational.

Because deur is a de-word.

In Dutch, every noun has a grammatical article:

• de for common-gender nouns
• het for neuter nouns

You simply have to learn nouns with their article:

• de deur = the door
• het raam = the window
• de tafel = the table

There is no simple rule that lets you predict all of them, so learners usually memorize the article together with the noun.

Yes, and that is actually very common.

Dutch often uses staan, liggen, and zitten in places where English just uses be.

For doors and windows, openstaan is extremely common:

• De deur staat open. = The door is open.

So both are possible:

• De deur is open
• De deur staat open

The version with staat open often sounds especially natural when talking about a door or window being left open.

Not exactly.

Dutch open is pronounced roughly like OH-puhn, with:

• a clearer long o
• a final -en that is not the same as English -en

The stress is on the first syllable:

• O-pen

Also, Dutch sluit has the ui sound, which many English speakers find difficult. That vowel does not exist in standard English, so it usually takes practice.

Yes, absolutely.

In fact, that is often the safest and most natural option for learners:

• De deur is open, maar ik sluit de deur straks.

This avoids the issue of object pronouns for things, which can be tricky in Dutch.

So if haar feels strange, repeating de deur is perfectly fine and often easier.