W naszej rodzinie pomagamy sobie nawzajem.

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

• rodzina = nominative singular, the dictionary form
• rodzinie = locative singular

So:

• rodzina = family
• w rodzinie = in the family

The adjective has to match too, so nasza changes to naszej.

Naszej is the feminine singular locative form of nasza (our).

It matches rodzinie, because adjectives in Polish agree with the noun in:

• gender
• number
• case

Since rodzina is:

• feminine
• singular
• here in the locative

the correct form is naszej.

So:

• nasza rodzina = our family
• w naszej rodzinie = in our family

Pomagamy is the 1st person plural present tense form of pomagać (to help).

So it means we help.

The ending -my tells you the subject is we, which is why Polish does not need the pronoun my here.

• pomagam = I help
• pomagasz = you help
• pomagamy = we help

Because Polish often drops subject pronouns when they are obvious from the verb ending.

Here, pomagamy already means we help, so my is unnecessary.

You could say:

• My pomagamy sobie nawzajem

but that usually adds emphasis, something like:

• We help each other.

The version without my is the most neutral and natural here.

Because pomagać takes the dative case, not the accusative.

In Polish, you help to someone, grammatically speaking.
So:

• pomagać komu? czemu? = to help whom? what? in the dative

The reflexive pronoun in the dative is sobie.

So:

• pomagamy sobie = we help ourselves / we help each other

But siebie is used in other cases, not the one required by pomagać, so it would be wrong here.

Because this sentence expresses a reciprocal action: the members of the family help one another.

Polish often uses the reflexive pronoun sobie together with nawzajem to express each other.

• pomagamy nam would not work here
• pomagamy sobie nawzajem is the natural way to say we help each other

So although sobie literally looks like to oneself/ourselves, in this structure it functions as part of the idea each other.

Nawzajem means mutually, reciprocally, or most naturally in English, each other.

So:

• pomagamy sobie nawzajem = we help each other

It makes the reciprocal meaning very clear.

Often, pomagamy sobie can already be understood as we help each other, especially from context.

But nawzajem makes it explicit and sounds very natural in general statements like this one.

Compare:

• Pomagamy sobie. = We help ourselves / we help each other, depending on context
• Pomagamy sobie nawzajem. = We help each other

So nawzajem is not always strictly required, but it is very useful for clarity.

Not necessarily. In Polish, just like in English, the present tense can describe:

• what is happening now
• a habit
• a general rule
• a characteristic of a group

Here it sounds like a general truth or family principle:

• In our family, we help each other.

So pomagamy here is more like we help each other as a rule, not only at this exact moment.

Because pomagać is imperfective, and it is the normal choice for:

• habits
• repeated actions
• general statements

This sentence describes an ongoing family pattern, so pomagać fits perfectly.

Pomóc is perfective, and it usually refers to a single completed act of helping.

Very roughly:

• pomagamy = we help / we are in the habit of helping
• pomożemy = we will help / we will manage to help once

Yes. Polish word order is fairly flexible, because endings carry a lot of the grammar.

The original sentence is neutral and very natural:

• W naszej rodzinie pomagamy sobie nawzajem.

Other orders are possible, for example:

• Pomagamy sobie nawzajem w naszej rodzinie.
• W naszej rodzinie sobie nawzajem pomagamy.

These may shift the emphasis slightly, but the basic meaning stays the same. For a learner, the original order is the safest and most idiomatic choice.

Because Polish does not have articles like English a or the.

So Polish simply says:

• w naszej rodzinie

and English supplies the natural article when translating:

• in our family

This is completely normal in Polish.

A rough English-friendly approximation is:

v NAH-shey roh-JEE-nyeh po-ma-GA-mi SOH-byeh nav-ZAH-yem

A few useful notes:

• w sounds like English v
• sz sounds like sh
• dzi/zie in rodzinie is a soft sound; JEE-nyeh is only an approximation
• j in Polish sounds like English y
• nawzajem has stress on ZA

As usual in Polish, the stress is normally on the second-to-last syllable:

• roDZInie
• pomagaGAmy
• nawZAjem