Mi prima quería acampar allí arriba, pero yo preferí bajar al campamento antes de que anocheciera.

Quería is the imperfect of querer, and here it presents your cousin’s wish as a background intention or ongoing desire: she wanted to camp up there.

If you said quiso, that would be the preterite, which often sounds more like she wanted / she tried / she decided to, as a completed event. In this sentence, quería fits better because it sets up her preference in contrast to the speaker’s later decision.

So the contrast is:

• Mi prima quería... = my cousin wanted to...
• yo preferí... = I chose / preferred to...

This is a very common imperfect + preterite contrast in narration.

Preferí is the preterite, so it shows a specific, completed choice in the past: I decided / I preferred to go down.

If you used prefería, it would sound more like a general or ongoing preference:

• preferí = I chose, at that moment
• prefería = I used to prefer / I was preferring / my preference was

In this sentence, the speaker is describing one concrete decision in a past situation, so preferí is the natural choice.

Yes, Spanish often leaves subject pronouns out because the verb ending already shows the person. So preferí already means I preferred.

But yo is included here for contrast:

• Mi prima quería...
• pero yo preferí...

That yo helps emphasize the difference between the two people:

• my cousin wanted one thing
• but I preferred something else

So it is not required, but it is very natural and useful for emphasis.

Allí arriba means up there.

It combines:

• allí = there, over there
• arriba = up / above

Together they give a clear idea of a place that is both:

• away from the speaker
• higher up

It is more specific than just arriba, because arriba only tells you the direction or relative height, while allí arriba points to a particular place.

These three words are related but not identical:

• ahí = there, near the person being spoken to
• allí = there, farther away, more specific
• allá = over there, often farther away or more vague

In this sentence, allí arriba suggests a definite place up there, not especially close to either speaker. That makes allí a very natural choice.

In real speech, some variation is possible depending on the speaker’s perspective, but allí arriba sounds completely normal.

Because they come after conjugated verbs and function like to camp and to go down in English.

Here:

• quería acampar = wanted to camp
• preferí bajar = preferred to go down

After verbs like querer, preferir, poder, deber, and many others, the second verb is usually left in the infinitive.

Al is just a + el contracted:

• a el campamento → al campamento

You use a here because bajar in this sentence means to go down to a place.

So:

• bajar al campamento = to go down to the camp / campsite

This is different from using a direct object. The speaker is moving toward a location, so a is needed.

Because antes de que introduces a subordinate clause, and after antes de que, Spanish normally uses the subjunctive:

• antes de que anocheciera = before it got dark

This structure is very common.

That said, antes de anochecer is also possible and natural. It is just more compact:

• antes de que anocheciera = before it got dark
• antes de anochecer = before dark / before nightfall

Both can work, but the version with antes de que is especially clear and explicit.

Because it comes after antes de que, which normally triggers the subjunctive.

Spanish often uses the subjunctive after expressions that refer to something not yet completed from the point of view of the main action, such as:

• antes de que
• para que
• sin que

Since the main narration is in the past, Spanish uses the imperfect subjunctive here:

• anocheciera

If the main verb were in the present or future, you would usually get the present subjunctive instead:

• prefiero bajar antes de que anochezca

It is the imperfect subjunctive of anochecer.

The verb anochecer means to get dark, to grow dark, or for night to fall.

The imperfect subjunctive has two standard forms in Spanish:

• anocheciera
• anocheciese

Both are correct. -ra forms like anocheciera are more common in everyday speech.

Because anochecer is often used impersonally.

In English, we usually say it got dark, where it is a dummy subject. Spanish does not need that kind of subject, so it simply says:

• anocheció
• anochecía
• anocheciera

So in antes de que anocheciera, the idea is simply before it got dark, without expressing any real subject.

Yes. Depending on context, campamento can mean:

• a camp
• a campsite
• an encampment
• a camping area

In Spain, you may also hear camping for a commercial campsite or campground. But campamento is perfectly normal if the idea is the camp area itself.

So in this sentence, bajar al campamento can naturally mean go down to the camp or go down to the campsite, depending on the situation.

The accent marks help show the correct stress and, in these cases, are part of the standard written forms.

• quería is stressed on -rí-
• preferí is stressed on the final -rí

They also help distinguish the correct verb forms in writing. For learners, it is useful to remember them as part of the full form:

• quería
• preferí

So yes, those accents are required, not optional.