Instruktorka mówi, że najpierw trzeba ustawić fotel i oba lusterka.

Instruktorka is the feminine form of instruktor. It tells you the instructor is a woman.

• instruktor = male instructor
• instruktorka = female instructor

Polish often marks the natural gender of professions more clearly than English does.

It can mean either, depending on context.

Polish present tense often covers both:

• English says
• English is saying

So Instruktorka mówi... can mean:

• The instructor says...
• The instructor is saying...

In a sentence like this, English usually uses says.

Że means that and introduces a subordinate clause.

So:

• Instruktorka mówi = The instructor says
• że najpierw trzeba ustawić... = that first you need to adjust...

It works very much like English that after verbs such as say, think, know, and see.

Because in Polish, a subordinate clause introduced by że normally takes a comma.

So:

• mówi, że...
• myślę, że...
• wiem, że...

This is standard Polish punctuation, even when English might sometimes omit that and therefore not show such a clear break.

Najpierw means first, first of all, or before anything else.

Its position is fairly flexible. You could also say:

• Najpierw trzeba ustawić fotel i oba lusterka.
• Trzeba najpierw ustawić fotel i oba lusterka.

The original word order is natural and emphasizes the sequence of actions.

Trzeba is an impersonal word meaning something like:

• it is necessary
• one must
• you need to
• you have to

Polish often uses trzeba for general instructions, rules, or advice without naming a specific subject.

So trzeba ustawić... literally means it is necessary to adjust..., but natural English is usually you need to adjust... or you have to adjust....

Because trzeba is normally followed by an infinitive.

This is a very common pattern:

• trzeba zrobić = you need to do
• trzeba poczekać = you need to wait
• trzeba ustawić = you need to set/adjust

So trzeba + infinitive is one of the basic Polish structures learners see early on.

This is a question of aspect.

• ustawić = perfective
• ustawiać = imperfective

Here ustawić is used because the sentence is about completing the action: getting the seat and mirrors into the correct position before doing something else.

Very roughly:

• ustawić = set/adjust into place
• ustawiać = be setting/adjusting, adjust repeatedly, or adjust in general

In driving instructions, a one-time completed action fits ustawić very well.

It can mean both, depending on context.

In general:

• fotel can mean armchair
• in vehicle contexts, it commonly means seat

So in a car-related sentence:

• ustawić fotel = adjust the seat

That is completely natural Polish.

They are the direct objects of ustawić, so they are in the accusative case.

However, with these nouns, the accusative looks the same as the nominative:

• fotel is masculine inanimate singular

  • nominative: fotel
  • accusative: fotel

• lusterka is neuter plural

  • nominative: lusterka
  • accusative: lusterka

So the case is accusative, but there is no visible ending change here.

Oba means both.
Dwa means two.

So:

• dwa lusterka = two mirrors
• oba lusterka = both mirrors

Oba is the right choice when referring to the whole pair, not just the number.

It also agrees grammatically with lusterka, which is a neuter plural noun. Compare:

• oba lusterka = both mirrors
• obie ręce = both hands (feminine plural)
• obaj studenci = both students (masculine personal plural)

You may also hear obydwa lusterka, which means the same thing.

Yes. The singular is lusterko, and the plural is lusterka.

Historically, lusterko is a diminutive of lustro (mirror), but in everyday Polish it is very commonly used for smaller mirrors, especially car mirrors. In that context, it sounds completely normal and not especially cute or childish.

So in driving-related language:

• lustro is possible in some contexts
• lusterko is often the more natural everyday choice for a car mirror