Nach dem Einbruch flieht der Einbrecher, bevor die Polizei kommt.

Because nach takes the dative case when it means after in a time expression.

• der Einbruch = nominative
• dem Einbruch = dative

So:

• nach dem Einbruch = after the break-in

This is a very common pattern in German:

• nach dem Essen = after the meal
• nach der Arbeit = after work
• nach dem Film = after the movie

They are related, but they mean different things:

• der Einbruch = the burglary / break-in (the event)
• der Einbrecher = the burglar (the person)

A useful pattern is that -er often makes a noun for a person who does something:

• arbeiten → der Arbeiter
• fahren → der Fahrer
• einbrechen → der Einbrecher

So Einbruch is the crime, and Einbrecher is the criminal.

This is because German main clauses follow the verb-second rule.

In this sentence, the first element is:

• Nach dem Einbruch

That takes the first position, so the finite verb must come next:

• Nach dem Einbruch flieht der Einbrecher

Even though der Einbrecher is the subject, it comes after the verb because the first position is already occupied.

You could also say:

• Der Einbrecher flieht nach dem Einbruch, bevor die Polizei kommt.

That is also correct, but the emphasis is slightly different.

It is in the nominative case because it is the subject of the main clause — the one doing the action of flieht.

So here:

• der Einbrecher flieht = the burglar flees

If it were a direct object, masculine der would usually change to den:

• Die Polizei sucht den Einbrecher.

That contrast is very useful:

• der Einbrecher = subject
• den Einbrecher = direct object

Because bevor introduces a subordinate clause, and in German, subordinate clauses are normally separated by a comma.

So:

• ..., bevor die Polizei kommt.

This comma is required in standard German.

Notice that there is not a comma after Nach dem Einbruch, because that is just a prepositional phrase at the beginning of the main clause, not a separate clause.

Because bevor is a subordinating conjunction. In German subordinate clauses, the finite verb usually goes to the end.

So:

• bevor die Polizei kommt

This is the normal subordinate-clause pattern:

• weil er müde ist
• dass sie heute kommt
• wenn die Polizei kommt
• bevor die Polizei kommt

A good rule to remember is:

• main clause: finite verb in second position
• subordinate clause: finite verb at the end

Because bevor and vor do different jobs.

• bevor = before as a conjunction; it introduces a clause
• vor = before / in front of as a preposition; it goes with a noun

In this sentence, what follows is a full clause:

• die Polizei kommt

So you need bevor:

• bevor die Polizei kommt

If you wanted to use vor, it would need a noun phrase, for example:

• vor der Polizei = before / in front of the police

In German, die Polizei is grammatically singular, even though it refers to a group of people.

So German says:

• die Polizei kommt

not:

• die Polizei kommen

This is different from English, where the police usually takes a plural verb.

If you want a clearly plural noun in German, you could say:

• die Polizisten kommen = the police officers are coming

Yes, both are in the present tense:

• flieht = present tense of fliehen
• kommt = present tense of kommen

German often uses the present tense where English might also use present, or sometimes future, if the time is clear from context.

So this sentence naturally means something like:

• After the break-in, the burglar flees before the police arrive.

The timing is clear from the context, so no special future form is needed.

Because all German nouns are capitalized.

So in this sentence:

• Einbruch = noun
• Einbrecher = noun
• Polizei = noun

That is why they all begin with capital letters.

This is one of the most noticeable spelling rules in German.

This sentence is good practice because it contains both patterns:

• ei is usually pronounced like English eye
• ie is usually pronounced like English ee

So:

• Einbruch → ei sounds like eye
• Einbrecher → same ei sound
• Polizei → final ei also sounds like eye
• flieht → ie sounds like ee

A very useful memory trick is:

• ei = eye
• ie = ee

Not necessarily. It simply means after the break-in.

It tells you the order of events:

1. the break-in happens
2. the burglar flees
3. the police come later

But it does not by itself say exactly how much time passes. If you wanted to emphasize immediacy, German could use other expressions such as:

• direkt nach dem Einbruch
• unmittelbar nach dem Einbruch

So nach dem Einbruch is neutral and simply marks what happens later in time.