W tej firmie każdy pracownik zna swoich współpracowników i rano mówi im dzień dobry.

Because after w meaning in for location, Polish uses the locative case.

The basic form is ta firma = this company.
In the locative, it changes to:

• ta → tej
• firma → firmie

So:

• w tej firmie = in this company

This is a very common pattern with w when it means location.

Because każdy means each or every, and in Polish it behaves as grammatically singular.

So you say:

• każdy pracownik zna = each employee knows

not

• każdy pracownik znają

Compare:

• każdy pracownik zna = each employee knows
• wszyscy pracownicy znają = all employees know

So even though the idea refers to many people, każdy makes the grammar singular.

They are similar, but not identical.

• każdy pracownik = each / every employee
• wszyscy pracownicy = all employees

Każdy pracownik looks at the group one person at a time.
Wszyscy pracownicy looks at the group as a whole.

In many contexts, both can translate naturally into English, but the grammar changes:

• Każdy pracownik zna...
• Wszyscy pracownicy znają...

Because in Polish:

• znać = to know a person, place, language, book, song, etc.
• wiedzieć = to know a fact, piece of information, or answer

So:

• zna pracowników = knows the employees
• wie, że firma jest duża = knows that the company is big

Since the sentence is about being acquainted with coworkers, znać is the correct verb.

Because Polish usually uses the reflexive possessive swój when something belongs to or is associated with the subject of the sentence.

Here the subject is każdy pracownik. So the natural form is:

• każdy pracownik zna swoich współpracowników

This means each employee knows his/her own coworkers.

If you used jego, jej, or ich, it could sound more ambiguous, as if you were talking about someone else’s coworkers rather than the subject’s.

This use of swój is very common and very important in Polish.

Because swoich has to match współpracowników.

Here współpracowników is:

• plural
• masculine personal
• accusative

With masculine-personal plural nouns in the accusative, adjectives and pronouns often take forms that look like the genitive plural. That is why you get:

• swoich współpracowników

not

• swoje współpracowniki or swoje współpracowników

So this is really about agreement with the noun.

Because znać takes the accusative case, and współpracowników is the accusative plural form here.

The forms are:

• współpracownicy = nominative plural
• współpracowników = accusative plural / genitive plural

For masculine personal nouns, the accusative plural usually looks the same as the genitive plural.

So:

• pracownicy znają współpracowników

not

• pracownicy znają współpracownicy

Because mówić in this meaning works like:

• mówić komuś coś = to say something to someone

The person you speak to is in the dative case.

So:

• im = to them

That is why the sentence has:

• mówi im dzień dobry = says good morning to them

If you used ich, that would be the wrong case here.

Yes. That is possible if the listener already knows who is being greeted.

• rano mówi dzień dobry = in the morning, he/she says good morning
• rano mówi im dzień dobry = in the morning, he/she says good morning to them

Adding im makes the target of the greeting explicit.

That is just the normal Polish way to express this idea.

Polish often uses mówić komuś plus the greeting:

• mówić komuś dzień dobry
• mówić komuś dobry wieczór
• mówić komuś cześć

So literally it is say good morning to someone, but functionally it means greet someone with good morning.

This is idiomatic and very common.

Because dzień dobry is a fixed greeting expression.

Even though dzień and dobry are ordinary words in other contexts, together as a greeting they are treated like a set phrase:

• Dzień dobry! = Good morning / Good day

After mówić, Polish still keeps the greeting in this fixed form:

• mówi dzień dobry
• powiedział dzień dobry

So learners should treat it as one expression.

Because rano is already an adverb meaning in the morning.

So you simply say:

• rano = in the morning

You do not need a preposition there.

Compare:

• Rano pracuję. = I work in the morning.
• Rano mówi im dzień dobry. = In the morning, he/she says good morning to them.

Yes. Polish word order is more flexible than English word order.

This sentence begins with:

• W tej firmie...

That puts the setting first: In this company...

You could also say:

• Każdy pracownik w tej firmie zna swoich współpracowników...

That is also correct, but the emphasis is slightly different.

The original version sounds natural because it first establishes the place, then tells you what happens there.

Because i here simply joins two parts with the same subject:

• każdy pracownik zna...
• i rano mówi...

In Polish, you normally do not put a comma before i when it joins two coordinated verbs or clauses like this.

So the sentence is correctly written without a comma.

Grammatically, pracownik is a masculine singular noun. But in a general statement like this, Polish often uses masculine forms generically.

So:

• każdy pracownik can mean every employee in a general sense

If you specifically mean a woman, you can say:

• pracownica = female employee

In modern Polish, some speakers prefer more explicitly inclusive wording in certain contexts, but the sentence you have is normal standard Polish.

Not always exactly, but it is close.

• współpracownik literally means someone you work together with
• In English, that can be coworker or colleague

In many contexts, coworker is the most direct translation.
Depending on tone and context, colleague may also work.

So in this sentence, coworkers is probably the most straightforward choice.