Ta stara kamienica ma ciężkie drzwi i głośny domofon.

Because kamienica is a feminine noun in Polish.

In Polish, demonstratives like this and adjectives like old must agree with the noun in gender, number, and case.

So in the nominative singular:

• masculine: ten stary
• feminine: ta stara
• neuter: to stare

Since kamienica is feminine, you get:

• ta stara kamienica

Kamienica usually means a traditional urban townhouse or apartment building, often an older multi-storey building, especially in a city.

It is not just any house. In Polish, dom is the general word for house, but kamienica suggests a specific kind of city building, often older and divided into flats. So it has a cultural and architectural nuance that simple English translations do not always fully capture.

Ma means has. It is the 3rd person singular form of the verb mieć (to have).

Conjugation of mieć in the present tense:

• ja mam — I have
• ty masz — you have
• on/ona/ono ma — he/she/it has
• my mamy — we have
• wy macie — you all have
• oni/one mają — they have

Since ta stara kamienica is a singular subject, the verb is ma.

Because drzwi is grammatically plural in Polish.

The word drzwi means door/doors, but in Polish it behaves as a plural-only noun. That means even when English uses singular door, Polish still uses the plural form drzwi.

Since the noun is plural, the adjective must also be plural:

• ciężkie drzwi — heavy door / heavy doors

The form ciężkie is the plural form used with non-masculine-personal nouns.

Yes. Drzwi is one of those Polish nouns that normally exist only in the plural.

Other common examples are:

• spodnie — trousers
• nożyczki — scissors
• okulary — glasses

So you do not normally say a singular form for drzwi in everyday standard Polish. Even if you are talking about one doorway or one set of doors, Polish still uses drzwi.

Because domofon is a masculine singular noun.

The adjective must agree with it, so:

• głośny — masculine singular
• domofon — masculine singular

That is why the phrase is:

• głośny domofon

A very useful comparison:

• stara kamienica — feminine singular
• głośny domofon — masculine singular
• ciężkie drzwi — plural

They are in the accusative, because they are the direct objects of ma (has).

So logically:

• kamienica ma co?
• The building has what?
• ciężkie drzwi i głośny domofon

However, in this sentence the forms look the same as the nominative:

• drzwi stays drzwi
• domofon stays domofon

Why?

1. drzwi is plural and here its accusative form looks the same as its nominative form.
2. domofon is a masculine inanimate noun, and masculine inanimate nouns usually have the same nominative and accusative singular.

So the objects are accusative, even though you do not see a spelling change.

Because Polish does not have articles like English the and a/an.

So:

• kamienica can mean a building or the building
• domofon can mean an intercom or the intercom

Context tells you which meaning is intended.

In this sentence, ta already means this, so it makes the noun definite enough:

• ta stara kamienica — this old building

Yes, in normal neutral Polish, adjectives usually come before the noun:

• stara kamienica
• ciężkie drzwi
• głośny domofon

It is possible to place an adjective after the noun in some cases, but that often sounds more literary, emphatic, or specialized. For a learner, the safest default is:

• adjective first
• noun second

A few helpful points:

• ci before a vowel sounds roughly like English ch but softer
• ę is a nasal vowel, often pronounced approximately like en/em depending on the sound after it
• rz usually sounds like the zh sound in measure
• ś is a soft sh sound
• ł sounds like English w

So roughly:

• ciężkie ≈ CHYEN-gkye
• drzwi ≈ zhvee or jvee depending on accent and speech
• głośny ≈ GWO-shnih
• domofon ≈ doh-MOH-fon

These are only approximations. The real Polish sounds are a bit different from English.

Because stary is just the basic dictionary form, usually the masculine singular nominative.

Adjectives change form depending on the noun they describe.

So:

• stary dom — an old house
• stara kamienica — an old building
• stare okno — an old window
• stare drzwi — old door/doors

In your sentence, kamienica is feminine, so stary changes to stara.

Yes, you could, and it would still be understandable, because Polish word order is fairly flexible.

But the original sentence:

• Ta stara kamienica ma ciężkie drzwi i głośny domofon.

is the most neutral and natural order for a learner.

If you move things around, you usually change the emphasis. For example:

• Ciężkie drzwi i głośny domofon ma ta stara kamienica.

This puts more focus on what the building has, almost like It’s this old building that has heavy doors and a loud intercom.

So the original version is the best default choice.