Learn Hardcore German: In der Stadt treffen sich die Jungen in einem Café, während die Alten lieber zu Hause bleiben. - In the city the young ones meet in a café, while the elderly prefer to stay at home.

Dative = location (where something is):
- In der Stadt treffen sich die Jungen. → They meet in the city (location).
Accusative = direction (where something is going to):
- Sie fahren in die Stadt. → They are going to the city (movement towards).

Here we are talking about where they meet (a place), so we use dative → „der Stadt“ (feminine dative singular).

Why do we say „treffen sich“ instead of just „treffen“?

German distinguishes between:

jemanden treffen = to meet someone (accusative object)
- Ich treffe meinen Freund im Café. → I meet my friend in the café.
sich treffen = to meet (each other), to arrange to meet
- Wir treffen uns im Café. → We meet (each other) in the café.

In the sentence, die Jungen are meeting each other, not some third person, so German normally uses the reflexive verb:

Die Jungen treffen sich in einem Café. → The young (people) meet (each other) in a café.

So „sich treffen“ is the natural choice here.

Why is the word order „In der Stadt treffen sich die Jungen …“ and not „In der Stadt die Jungen treffen sich …“?

Main clauses in German follow the verb‑second rule:

Exactly one element (subject, adverbial, object, etc.) can stand in position 1.
The conjugated verb must be in position 2.

In the sentence:

Position 1: In der Stadt (adverbial)
Position 2: treffen (conjugated verb)
Then the rest: sich die Jungen in einem Café

So „In der Stadt treffen sich die Jungen …“ is correct.

„In der Stadt die Jungen treffen sich …“ is wrong because then the verb is in third position.

You could also say:

Die Jungen treffen sich in der Stadt in einem Café. (subject first)
In der Stadt treffen die Jungen sich in einem Café.

Both are grammatically fine; they just emphasize different parts slightly.

What exactly does „die Jungen“ mean here? Boys, or just “young people”?

In this sentence, „die Jungen“ is best understood as “the young (people)”, i.e. the younger generation, parallel to „die Alten“ = “the old (people)”.

It does not have to mean only male boys here. It’s a nominalized adjective from jung and can refer to young people of any gender, especially in a contrast like:

die Jungen vs. die Alten

So:

die Jungen → the young people
die Alten → the old people

Why are „Jungen“ and „Alten“ capitalized?

They are adjectives used as nouns (nominalized adjectives). In German, if an adjective is used as a noun, it:

gets a capital letter, and
declines like an adjective, but with a noun’s article:

Examples:

die Reichen → the rich (people)
der Alte → the old man
die Alten → the old (people)
die Jungen → the young (people)

So „Jungen“ (from jung) and „Alten“ (from alt) are capitalized for this reason.

Why is it „in einem Café“ and not „in ein Café“?

Again it’s the location vs. direction contrast with „in“:

Location → dative:
- Sie sitzen in einem Café. → They are (sitting) in a café.
Direction → accusative:
- Sie gehen in ein Café. → They go into a café.

In the sentence, the meeting takes place in the café (location), so „Café“ is in the dative:

Neuter singular: das Café
Dative: in einem Café

Do I always need a comma before „während“?

Here „während“ is used as a subordinating conjunction (“while/whereas”) introducing a full clause:

…, während die Alten lieber zu Hause bleiben.

In this use:

It must have a comma before it, and
It sends the finite verb to the end of its clause.

So the comma is mandatory in this sentence.

(There is also während + Genitive as a preposition meaning “during”, e.g. während des Urlaubs, but that’s a different structure.)

Why is the verb „bleiben“ at the very end of „während die Alten lieber zu Hause bleiben“?

Because „während“ here is a subordinating conjunction, and subordinate clauses in German have the conjugated verb at the end.

Word order pattern:

Subordinating conjunction
- subject
  - … + verb (at the end)

In this clause:

Conjunction: während
Subject: die Alten
Adverb: lieber
Adverbial: zu Hause
Verb (at the end): bleiben

→ während die Alten lieber zu Hause bleiben

What does „lieber“ mean here, and how is it used?

„lieber“ is the comparative form of „gern“:

gern → like doing something
lieber → prefer doing something (more than some other option)
am liebsten → like most of all

In the sentence:

die Alten lieber zu Hause bleiben

means roughly:

“the old people prefer to stay at home”
literally: “the old (people) stay more gladly at home”

Grammar-wise, „lieber“ is an adverb that modifies the verb bleiben:

Sie bleiben lieber zu Hause. → They prefer to stay at home.

What’s the difference between „zu Hause“ and „nach Hause“?

They encode location vs. direction:

zu Hause = at home (location)
- Ich bin zu Hause. → I am at home.
nach Hause = (to) home (direction, going there)
- Ich gehe nach Hause. → I’m going home.

In the sentence, the Alten are staying (no movement), so we use zu Hause:

… lieber zu Hause bleiben. → prefer to stay at home.

Why is it „zu Hause“ with an -e at the end of „Haus“?

„zu Hause“ is a fixed idiomatic expression:

zu Hause → at home
historically it’s a dative form: zu dem Hause

The form „Hause“ (with -e) is now mostly archaic and survives mainly in set phrases:

zu Hause (at home)
nach Hause (home, homewards)
von Hause aus (by background, originally)

Outside such expressions, you normally use „Haus“:

Ich stehe vor dem Haus.
Das Haus ist groß.

Could the word order in the second part be „während die Alten zu Hause lieber bleiben“?

Yes, that is grammatically correct:

während die Alten lieber zu Hause bleiben
während die Alten zu Hause lieber bleiben

Both respect the rule that the conjugated verb (bleiben) is at the end of the subordinate clause. The difference is only in rhythm and slight emphasis:

… lieber zu Hause bleiben sounds a bit more natural and is more common.
… zu Hause lieber bleiben puts a tiny bit more emphasis on zu Hause.