Vor der Abfahrt muss ich den Rückspiegel neu einstellen.

German main clauses follow the verb-second rule. That means the conjugated verb must be in the second position.

Here, Vor der Abfahrt is placed first for emphasis or context, so the verb muss has to come next:

• Vor der Abfahrt = position 1
• muss = position 2
• ich = subject after the verb

If you start with the subject instead, you get:

• Ich muss vor der Abfahrt den Rückspiegel neu einstellen.

Both are correct.

The basic noun is die Abfahrt. But after vor in this sentence, it changes to der Abfahrt because vor takes the dative here.

So:

• nominative: die Abfahrt
• dative: der Abfahrt

This happens because vor is being used in a time expression meaning before the departure.

No. Vor is a two-way preposition (Wechselpräposition), so it can take either:

• dative for location or time
• accusative for movement toward a position

In this sentence, vor der Abfahrt is a time expression, so it uses the dative.

Compare:

• vor der Abfahrt = before the departure → dative
• Ich stelle mich vor den Bus. = I move to a position in front of the bus. → accusative

Here, Abfahrt means departure.

Depending on context, it can refer to:

• the departure of a vehicle
• the start of a trip
• a scheduled departure time

So Vor der Abfahrt means before leaving / before the departure.

Because Rückspiegel is the direct object of einstellen, and direct objects usually go in the accusative case.

The noun is masculine:

• nominative: der Rückspiegel
• accusative: den Rückspiegel

So:

• Ich stelle den Rückspiegel ein.

German compound nouns usually take their gender from the last part of the compound.

• der Spiegel = mirror
• der Rückspiegel = rear-view mirror

Since Spiegel is masculine, Rückspiegel is also masculine.

Here, neu einstellen means to readjust or to adjust again.

The word neu literally means new, but with verbs like einstellen, it often has the sense of again / afresh / correctly from the start.

So in this sentence, it means something like:

• I have to readjust the rear-view mirror before departure.

Yes, einstellen is a separable verb.

On its own in a normal main clause, it separates:

• Ich stelle den Rückspiegel neu ein.

But after a modal verb like müssen, the second verb goes to the end in the full infinitive form, so it does not split:

• Ich muss den Rückspiegel neu einstellen.

That is why you see einstellen together here.

Because neu modifies the action of einstellen. In a verb phrase with an infinitive at the end, adverbs like this usually come before the infinitive:

• den Rückspiegel neu einstellen

If the separable verb is split in a main clause, neu still stays with the verb phrase:

• Ich stelle den Rückspiegel neu ein.

So the position of neu is normal and natural.

Yes, absolutely. That is a very natural alternative.

Compare:

• Vor der Abfahrt muss ich den Rückspiegel neu einstellen.
• Bevor ich abfahre, muss ich den Rückspiegel neu einstellen.

The first version uses a noun phrase (vor der Abfahrt = before departure).

The second version uses a subordinate clause (bevor ich abfahre = before I leave).

Both are correct; the first is a bit more compact.

Because all nouns are capitalized in German.

So in this sentence:

• Abfahrt is a noun
• Rückspiegel is a noun

That is why they begin with capital letters. This is a standard rule in German spelling.