Learn Hardcore Polish: Planują długie małżeństwo i marzą o domu, w którym będą razem. - They are planning a long marriage and dream of a house in which they will be together.

Planują and marzą both end in -ą, which marks 3rd person plural (they).
Because of that, adding oni / one (they) is usually unnecessary:
Oni planują długie małżeństwo sounds heavier and is used only for emphasis or contrast (e.g. Oni planują, a my nie – They are planning, and we are not).

So the sentence naturally omits they; the subject is understood from the verb forms.

What tense are planują and marzą, and can they refer to the future?

Planują (from planować) and marzą (from marzyć) are in the present tense of imperfective verbs.

They can mean:

Right now / these days:
Planują długie małżeństwo – They are (now) planning a long marriage.
Or a general or near future intention (similar to English they’re going to/they plan to): context can make it future-like.

Imperfective present often covers “present” + “planned/ongoing future” in Polish.
By contrast, the explicit future is shown with będą (they will be) in będą razem.

What is the aspect of planować and marzyć, and could we use perfective forms instead?

Planować and marzyć are imperfective verbs.
Imperfective is used for:
- ongoing processes,
- repeated actions,
- general states and intentions.

Perfective partners would be, for example:

zaplanować – to plan something fully, to have it all planned (a completed act),
there isn’t a single natural perfective partner for marzyć in the same everyday sense; forms like zamarzyć or wymarzyć are used in more specific or idiomatic contexts.

In this sentence we talk about ongoing intentions and dreams, so imperfective is correct and natural:

Planują / marzą – they are in the process of planning / dreaming. Using perfective here would sound odd or change the meaning to a single completed act, which is not intended.

Why is it długie małżeństwo and not długą małżeństwo?

Because małżeństwo is neuter, and the adjective must agree with it in gender, number, and case.

Nominative singular:
- masculine: długi dom
- feminine: długa książka
- neuter: długie małżeństwo

Here małżeństwo is the direct object (accusative singular), and for neuter nouns, nominative = accusative in form.
So we use długie (neuter) to match małżeństwo, not długą (feminine).

Why is małżeństwo in the accusative case here?

Małżeństwo is the direct object of the verb planują:

Co planują? – What are they planning? → długie małżeństwo.

Answers to co? kogo? after many verbs are in the accusative.
For neuter nouns like małżeństwo, nominative and accusative look the same (małżeństwo), which can hide the case change, but grammatically it is accusative.

Why do we say marzyć o czymś (with o) instead of just using a direct object?

Polish verb government is different from English:

English: to dream *of/about something or sometimes *dream something.
Polish: marzyć o + locative is the standard pattern:
- marzyć o domu – to dream of a house/home,
- marzyć o podróży – to dream of a trip.

You cannot say *marzyć dom; that sounds ungrammatical.
The preposition o is simply part of how marzyć works in Polish.

Why is it o domu and not o dom?

Because o in the sense of “about / of (dreaming of something)” requires the locative case.

The noun dom (house/home) declines like this (singular):

Nominative: dom
Genitive: domu
Dative: domowi
Accusative: dom
Instrumental: domem
Locative: domu

With o + locative:

o kim? o czym? – o domu.

So o domu is locative, not nominative.

Note: domu also happens to be the genitive form, so the ending -u is ambiguous; only context (the preposition o) tells you this is locative here.

In w którym, what does którym agree with, and why is it in that form?

Którym is a relative pronoun (a form of który) and it must:

refer back to dom / domu,
match it in gender and number,
take the case required by the preposition in its own clause.

Here:

Antecedent: dom – masculine singular.
Preposition: w (in), which normally takes locative (for static location: in a place).

So we need masculine singular locative of który:

masculine singular locative: (w) którym.

That’s why we say w którym będą razem – in which they will be together.

Why do we say w którym instead of repeating domu again?

Using a relative pronoun is the natural way in Polish to avoid repetition and connect clauses:

marzą o domu, w którym będą razem
literally: they dream of a house, in which they will be together.

If you repeated the noun:

marzą o domu, w domu będą razem – they dream of a house, in the house they will be together

this sounds clumsy and less clearly linked; it feels like two separate statements rather than one refined thought.
W którym neatly ties the subordinate clause back to domu.

Why is there a comma before w którym będą razem?

Because w którym będą razem is a subordinate (relative) clause describing domu.

Polish punctuation rules require a comma before most subordinate clauses, including those introduced by:

relative pronouns (który, jaki, etc.),
conjunctions like że, żeby, gdy, chociaż, etc.

So:

marzą o domu, w którym będą razem
Main clause: marzą o domu
Subordinate relative clause: w którym będą razem (describes what kind of house).

Hence the comma.

Could we say gdzie będą razem instead of w którym będą razem?

Yes, you can say:

Marzą o domu, gdzie będą razem.

This is understandable and used in speech, but:

w którym is more precise and standard written style,
gdzie is a relative adverb (“where”), less tightly bound to dom as a noun.

Nuance:

w którym strongly ties the clause to that house specifically.
gdzie can sound a bit broader or more informal, like a place where they’ll be together.

For most everyday purposes, both are fine, but w którym is the textbook choice here.

Why is it będą razem (future tense) and not present są razem?

The sentence talks about their future hopes connected to the house:

Planują… i marzą o domu, w którym będą razem.

So:

będą – future of być (to be),
razem – together.

Using są razem (are together) would mean they are already together now in that house, which contradicts the idea that this is something they only dream of.

Future tense matches the idea of a house they don’t yet have, where they will be together in the future.

What exactly is razem, and can we move it elsewhere in the clause?

Razem is an adverb meaning “together”.

Normal word order:

będą razem – they will be together.

You can move it a bit:

razem będą – possible, often used to emphasise “together” slightly.
będą tam razem – they will be there together.

But in this short clause, będą razem is the most neutral and common order. Putting razem somewhere very unusual (e.g. breaking w którym and będą) would sound odd.

Is długie małżeństwo a natural phrase in Polish? It sounds a bit strange from an English point of view.

Yes, długie małżeństwo (a long marriage) is natural Polish.
You’ll also often see:

długie i szczęśliwe małżeństwo – a long and happy marriage.

What’s slightly unusual for English speakers is “planning” a long marriage, because in English we usually say we hope for or want a long marriage, not that we plan it.

In Polish:

Planują długie małżeństwo suggests they envision / intend their marriage to last long; it’s understandable and idiomatic enough, especially in a more figurative or romantic context.

Can we change the word order to Marzą o domu i planują długie małżeństwo?

Yes, that sentence is grammatically correct:

Marzą o domu i planują długie małżeństwo.

Word order in Polish is relatively flexible. The change mostly affects which action feels more foregrounded:

Planują… i marzą… – first emphasises planning, then dreaming.
Marzą… i planują… – first emphasises dreaming.

Context would decide which sounds more natural, but both are acceptable Polish.