Jeden lokator z parteru zawsze mówi nam dzień dobry i pomaga nosić ciężkie torby.

Both ideas are possible.

Jeden literally means one, but in real Polish it can also help introduce someone as one resident / a certain resident. Since Polish has no articles, words like jeden sometimes do part of the job that English a/an does.

So jeden lokator can mean:

• one resident
• a resident
• one particular resident

It often adds a slight sense of this one person rather than just a completely neutral a resident.

Lokator means someone who lives in a place, usually with the idea of a tenant, lodger, or occupant.

It is not always exactly the same as resident in the broadest English sense. A very general word for resident is mieszkaniec, but lokator often suggests someone living in a building or apartment, especially as an occupant or renter.

Because z parteru means from the ground floor, while na parterze means on the ground floor.

In this sentence, the resident is being identified by where he is from in the building:

• lokator z parteru = the resident from the ground floor

If you were talking about location, you would use:

• On jest na parterze = He is on the ground floor

So:

• z + Genitive = from
• na + Locative = on / at

Because after z in this meaning, Polish uses the genitive case.

The dictionary form is parter. After z, it changes to parteru.

So:

• parter = ground floor
• z parteru = from the ground floor

This is a very common pattern:

• z domu = from the house
• z biura = from the office
• z parteru = from the ground floor

Because both mówić and pomagać usually take the person in the dative case.

Here:

• nam = to us / for us in the dative
• nas would be accusative or genitive, so it would not fit here

Examples:

• mówi nam dzień dobry = he says hello to us
• pomaga nam nosić torby = he helps us carry bags

So nam is correct because the actions are directed to us or done for us, not directly acting on us as a direct object.

It is a normal Polish way to express greeting someone.

Literally, it is close to:

• says good day to us

But naturally it means:

• says hello to us
• greets us with dzień dobry

The phrase dzień dobry is a fixed greeting, and after mówić it stays unchanged:

• mówić komuś dzień dobry = to say dzień dobry to someone

You may also hear:

• powiedzieć komuś dzień dobry = to say hello to someone once, as a completed act

Because dzień dobry works as a fixed expression.

Even though it literally contains two words that have their own grammar, as a greeting it behaves like one set phrase. In sentences like this, Polish normally keeps it unchanged:

• Mówi nam dzień dobry
• Powiedział mi dzień dobry

Learners often try to analyze it word by word, but it is better to learn it as one greeting formula.

Because in Polish, pomagać can be followed by an infinitive to mean help to do something.

So:

• pomaga nosić torby = he helps carry bags

This is a very common structure:

• pomaga gotować = helps cook
• pomaga sprzątać = helps clean
• pomaga nosić torby = helps carry bags

You can think of it as:

• he helps [to carry]

Because nosić fits repeated or habitual carrying, while nieść usually refers to carrying something in one specific instance.

Here the sentence describes a usual habit:

• he always says hello
• he helps carry heavy bags

So nosić is natural because it suggests a repeated or general activity.

Very roughly:

• nosić = carry regularly / carry around / carry in general
• nieść = carry right now / carry on one occasion

Because the whole sentence is about what he always does, nosić is the better choice.

Because torby is the direct object of nosić, so it is in the accusative plural. For non-masculine-personal plural nouns, the accusative plural looks the same as the nominative plural.

So:

• torby = bags
• ciężkie torby = heavy bags

The adjective must agree with the noun:

• ciężkie matches plural torby

A useful comparison:

• singular: ciężką torbę
• plural: ciężkie torby

So the plural may look simpler here because nominative and accusative have the same form.

Zawsze means always, and here it shows that the actions are habitual.

The word order is fairly neutral:

• Jeden lokator z parteru zawsze mówi nam dzień dobry i pomaga nosić ciężkie torby.

Polish word order is flexible, so you can move zawsze for emphasis, but the neutral placement before the verb is very common.

For example, a different order might sound more marked:

• Jeden lokator z parteru mówi nam zawsze dzień dobry...

That is possible, but the original version is more natural as a basic statement.

Because in Polish, the present tense is exactly what you use for habitual or repeated actions.

So:

• mówi = says / speaks
• pomaga = helps

With zawsze, the meaning becomes:

• he always says
• he always helps

This is the normal way to describe habits in Polish, just as English uses the present tense for habits:

• He always says hello
• He helps carry heavy bags

So there is nothing unusual here: present tense + zawsze = regular repeated behavior.