Wie monteert de kast nadat we hem hebben opgemeten?

Yes. In this sentence, wie means who and it is the subject of the main clause:

Wie monteert de kast ... ? = Who assembles/is going to assemble the cabinet ... ?

You can tell it is the subject because it comes directly before the finite verb monteert. If wie were the object, the structure would be different.

Monteren is the infinitive, meaning to assemble / to install / to mount.

Here the subject is wie, which behaves like he/she/it for verb agreement, so Dutch uses the third-person singular form:

• ik monteer
• jij monteert
• hij/zij/het monteert
• wie monteert

So monteert is simply the correctly conjugated present-tense form.

Yes. Dutch often uses the present tense for future situations when the context already makes the future meaning clear.

So Wie monteert de kast nadat we hem hebben opgemeten? can very naturally mean:

• Who assembles the cabinet after we’ve measured it?
• or Who will assemble the cabinet after we’ve measured it?

Dutch does have a future form with zullen, for example Wie zal de kast monteren ... ?, but that is not necessary here and can sound more marked or more predictive.

Because kast is a de-word in Dutch. Dutch nouns take either de or het, and this usually has to be learned with the noun.

So:

• de kast = correct
• het kast = incorrect

English speakers often want a simple rule, but for many nouns you just have to memorize the article as part of the word.

Nadat means after when it introduces a full clause with its own subject and verb.

Here it introduces:

nadat we hem hebben opgemeten

That clause has:

• subject: we
• object: hem
• verbs: hebben opgemeten

By contrast, na is a preposition and is followed by a noun phrase, not a full clause:

• na het opmeten = after measuring
• na de meting = after the measurement

So:

• nadat we hem hebben opgemeten = after we have measured it
• na het opmeten = after measuring

Because nadat introduces a subordinate clause, and in Dutch subordinate clauses the verbs typically move to the end.

So the order is:

• nadat
• we = subject
• hem = object
• hebben opgemeten = verb cluster at the end

That gives:

nadat we hem hebben opgemeten

Not:

nadat we hebben hem opgemeten

For English speakers, this is one of the most important Dutch word-order patterns to get used to.

Meten means to measure in a general sense.

Opmeten often means to measure up, to take measurements, or to measure something carefully for size/dimensions, especially when that measurement will be used for fitting, building, ordering, or installing something.

So in a furniture context, opmeten is very natural because you are taking the dimensions before the cabinet is assembled or installed.

Yes. Opmeten is a separable verb.

That means:

• in the infinitive, it stays together: opmeten
• in some finite forms, it splits: We meten de kast op
• in the past participle, ge goes between the prefix and the verb stem: op + ge + meten = opgemeten

So:

• infinitive: opmeten
• present main clause: we meten hem op
• past participle: opgemeten

That is why you get hebben opgemeten.

Dutch perfect tenses use either hebben or zijn as the auxiliary.
Opmeten normally takes hebben, because it is a regular transitive action done to an object:

we hebben hem opgemeten

Verbs that take zijn are often verbs of movement or change of state, such as:

• gaan → is gegaan
• komen → is gekomen
• worden → is geworden

But opmeten is not one of those, so hebben is correct.

Dutch does not use it in the same all-purpose way that English does.

Here hem refers back to de kast. For singular non-neuter nouns, Dutch often uses a personal pronoun such as hem or haar, rather than het.

A useful learner shortcut is:

• het-word nouns often go with het
• de-word nouns often go with hem/haar or sometimes die

One extra complication: traditional grammatical gender and everyday spoken usage do not always line up neatly. With inanimate de-words, many speakers in the Netherlands commonly use hem, while some speakers or styles may use haar for nouns that are historically feminine. You may also hear people avoid the issue by saying die or by repeating the noun.

So in this sentence, hem is a natural way to refer back to de kast.

Hebben opgemeten is the present perfect.

It is used because the measuring is understood as completed before the assembling. In other words:

1. first we measure the cabinet
2. then someone assembles it

Dutch often uses the perfect after nadat to make that completed-before relationship clear.

So:

nadat we hem hebben opgemeten
means roughly
after we have measured it / after we’ve measured it

Depending on the wider context, English might also translate this with after we measured it or after we had measured it, but the Dutch form here is perfectly natural.

It can cover both ideas, depending on context.

In a furniture context, monteren can mean:

• to assemble
• to put together
• to install / fit

So if the meaning shown to the learner is assemble, that is a good translation here. But in real life the Dutch verb can be slightly broader than the English word assemble.