Learn Hardcore German: Meine Schwester ist ziemlich nervös vor der Prüfung. - My sister is quite nervous before the exam.

Because vor is a two-way preposition that takes the dative case when it expresses location or a point in time. Prüfung is feminine, and the dative feminine definite article is der. So: vor der Prüfung. In the nominative/accusative it would be die Prüfung.

Indefinite version: vor einer Prüfung.
Note: der here is dative feminine (not genitive), triggered by vor.

Can I use “bevor” instead of “vor der Prüfung”?

Only if you follow it with a full clause. Bevor is a conjunction, not a preposition.

With a preposition: vor der Prüfung (before the exam).
With a clause: …, bevor die Prüfung beginnt. (…, before the exam begins.)

Does “vor” ever take the accusative?

Yes, as a two-way preposition it takes:

Dative for location/time point: vor der Schule, vor der Prüfung, vor drei Tagen.
Accusative for motion/direction: Sie geht vor das Haus. (She goes to the front of the house.)

Why doesn’t “nervös” have an ending here?

Because it’s a predicate adjective after the linking verb sein. Predicate adjectives in German do not take endings: Sie ist nervös.

With a noun, you would add an ending: eine nervöse Schwester.

What does “ziemlich” mean here—how strong is it compared to “sehr”?

Ziemlich means “quite/pretty/rather.” It’s weaker and more subjective than sehr (“very”). Rough scale:

eher < ziemlich ≈ recht < sehr < total/überaus. Colloquial alternatives: ganz schön nervös, echt nervös.

Where can I place “vor der Prüfung” and “ziemlich” in the sentence?

Several natural options:

Meine Schwester ist ziemlich nervös vor der Prüfung.
Meine Schwester ist vor der Prüfung ziemlich nervös.
Vor der Prüfung ist meine Schwester ziemlich nervös. (fronted time phrase → verb still in position 2) All are correct; moving phrases shifts emphasis slightly.

Why is it “Meine Schwester” and not “Mein Schwester”?

Schwester is feminine. Possessive determiners take an -e in the nominative feminine singular: meine Schwester.

Other nominative patterns: mein Bruder (masc.), mein Kind (neut.), meine Geschwister (plural).

How would it change if I talk about my brother instead?

Use the masculine nominative: Mein Bruder ist ziemlich nervös vor der Prüfung.

How do I say “during” or “after” the exam?

During: während der Prüfung (genitive in standard German).
After: nach der Prüfung (dative).

What if there are multiple exams?

Use the dative plural with article den and add -n to the noun:

vor den Prüfungen (before the exams).

Does “vor” here mean “before” in time or “in front of”?

Time. Vor can mean both, but context decides:

Temporal: vor der Prüfung (before the exam).
Spatial: vor dem Haus (in front of the house).

Can I drop the article and say “vor Prüfung”?

Not in standard usage. You’d say:

Specific: vor der Prüfung.
Non-specific: vor einer Prüfung.
Generic plural: vor Prüfungen.

What if I want to say “She gets/becomes nervous before the exam”?

Use werden: Sie wird vor der Prüfung nervös. That expresses a change of state.

Any quick pronunciation tips for “nervös” and “Prüfung”?

ö in nervös: round your lips while saying something like “eh”; the vowel is long here.
ü in Prüfung: say “ee” with rounded lips.
v is pronounced like English “f”: Prüfung → “PRÜ-fung”.
Final -ng is a velar nasal [ŋ], no hard “g” sound.