Na egzaminie trzeba było zatrzymać się przed znakiem i popatrzeć w lusterko.

Na egzaminie means on the exam / during the exam. After na in this meaning, Polish uses the locative case, so egzamin becomes egzaminie.

Compare:

• egzamin = exam
• na egzaminie = on the exam / during the exam

This is a very common pattern:

• na lekcji = in class
• na spotkaniu = at the meeting
• na imprezie = at the party

So here na egzaminie gives the setting: this happened during the exam.

Trzeba było means something like it was necessary, one had to, or you had to.

• trzeba = it is necessary / one must
• było = was

Together, they form a past expression:

• trzeba = you have to / one must
• trzeba było = you had to / it was necessary to

This is an impersonal construction, which means it does not name a specific subject such as I, you, or they. English often translates it with you had to, but in Polish it is more like it was required.

Because trzeba is used in an impersonal structure. In Polish, impersonal expressions like this typically use było in the past, regardless of who was involved.

So:

• trzeba = one must / it is necessary
• trzeba było = it was necessary / one had to

You do not change było to match a person:

• not trzeba byłem
• not trzeba byli

The form stays było.

Because after trzeba było, Polish usually uses an infinitive to say what had to be done.

So the structure is:

• trzeba było + infinitive

Examples:

• trzeba było czekać = you had to wait
• trzeba było podpisać = you had to sign
• trzeba było zatrzymać się = you had to stop
• trzeba było popatrzeć = you had to look

This is very normal and natural in Polish.

Because zatrzymać się means to stop, while zatrzymać without się usually means to stop something/someone or to detain.

Compare:

• zatrzymać samochód = to stop the car
• zatrzymać przestępcę = to detain a criminal
• zatrzymać się = to stop oneself / to come to a stop

In this sentence, the person taking the exam had to stop themselves/the vehicle, so zatrzymać się is the correct form.

Przed here means in front of / before, and with this meaning of location it takes the instrumental case.

So:

• znak = sign
• przed znakiem = in front of the sign / before the sign

The instrumental singular of znak is znakiem.

This is a useful pattern:

• przed domem = in front of the house
• przed szkołą = in front of the school
• przed światłami = before the traffic lights

In a driving-test context, przed znakiem most naturally means before the sign.

Great question. W can take either the locative or the accusative, depending on meaning.

• w + locative usually expresses location: in, inside
• w + accusative can express direction, but also appears with some verbs of looking

Here, with popatrzeć w lusterko, Polish uses w + accusative after a verb of looking to mean look into / at something.

So:

• lusterko is nominative/accusative singular
• w lusterko = into the mirror / at the mirror

This is similar to:

• spojrzeć w okno = look into the window
• patrzeć w ekran = look at the screen

So although w often does take the locative, after verbs like popatrzeć it is very common to see w + accusative.

They are related, but not identical.

• patrzeć = to look, to be looking, to watch
  This is usually imperfective, so it can describe an ongoing action.
• popatrzeć = to look for a moment
  This is perfective, often suggesting a brief or complete act of looking.
• spojrzeć = to glance / to cast a look
  Also perfective, often slightly more like glance than look.

In this sentence, popatrzeć w lusterko suggests a single completed action: look in the mirror.

That fits the driving-test situation well, because the sentence describes required steps:

1. stop before the sign
2. look in the mirror

Lusterko is a diminutive form of lustro.

• lustro = mirror
• lusterko = little mirror

But in practice, lusterko is the normal word for a car mirror, especially a side mirror or rear-view mirror in everyday speech. So even though it literally looks like small mirror, it is often just the most natural word in this context.

In a driving sentence, w lusterko sounds very natural.

Yes. I means and, so both actions are part of what was required:

• zatrzymać się przed znakiem = stop before the sign
• i popatrzeć w lusterko = and look in the mirror

Because both infinitives depend on trzeba było, the sense is: You had to stop before the sign and look in the mirror.

Not completely. Polish word order is fairly flexible, although some versions sound more natural than others.

The original sentence is very natural:

• Na egzaminie trzeba było zatrzymać się przed znakiem i popatrzeć w lusterko.

You could also say:

• Trzeba było na egzaminie zatrzymać się przed znakiem i popatrzeć w lusterko.

But that sounds a bit less neutral, because it shifts the focus slightly.

Polish often places background information like na egzaminie near the beginning, which is why the original version sounds so natural.

Yes, but it changes the structure and slightly changes the feel.

For example:

• Na egzaminie trzeba było zatrzymać się przed znakiem...
• Na egzaminie trzeba było is impersonal: it was necessary / one had to
• Na egzaminie musiałeś zatrzymać się przed znakiem... = On the exam, you had to stop before the sign...

So:

• trzeba było = more general, impersonal
• musiałeś / musiałam / musieli etc. = personal, tied to a specific subject

In instructions, rules, or general descriptions of requirements, trzeba było is very common.

It describes required actions in a specific past situation, and the infinitives chosen suggest single completed actions.

That is especially clear from:

• zatrzymać się — perfective
• popatrzeć — perfective

Perfective verbs often present actions as complete wholes. In this sentence, the idea is not you had to be stopping or you had to be looking continuously, but rather:

• stop
• look

So the sentence presents the required steps as complete actions during the exam.

Yes, and context decides which English translation sounds best.

In Polish, przed often covers both:

• in front of
• before

In a driving context, zatrzymać się przed znakiem usually means stop before the sign, because the important idea is position relative to the sign on the road.

In another context, przed znakiem could be translated more literally as in front of the sign. English just chooses the wording that best fits the situation.