Wenn der Rollladen nachts Lärm macht, schließe ich das Fenster ganz.

Wenn introduces a subordinate clause and can mean either if or when, depending on context.

In this sentence, Wenn der Rollladen nachts Lärm macht... could be understood as:

• If the shutter makes noise at night...
• When the shutter makes noise at night...

German often uses wenn in situations where English would choose either if or when. The exact meaning comes from context.

Because wenn der Rollladen nachts Lärm macht is a subordinate clause.

In German, subordinate clauses usually send the conjugated verb to the end:

• wenn
  • subject + other information + verb
• wenn der Rollladen nachts Lärm macht

That is one of the most important word-order patterns in German.

When a subordinate clause comes first, the main clause still follows the normal German verb-second rule.

The first position in the sentence is already occupied by the whole wenn clause:

• Wenn der Rollladen nachts Lärm macht, ...

So in the main clause, the verb must come next:

• schließe ich das Fenster ganz

This is why you get:

• Wenn ..., schließe ich ...

and not:

• Wenn ..., ich schließe ...

Der Rollladen is the subject of the subordinate clause, so it is in the nominative case.

• der Rollladen = the shutter / roller shutter

The noun Rollladen is masculine, so its nominative singular article is der.

Rollladen usually means an exterior roller shutter or rolling shutter on a window.

It is not the same as:

• Vorhang = curtain
• Jalousie = blind
• Fensterladen = shutter

A Rollladen is the kind that can be pulled down or rolled up.

Also, learners often notice the spelling: Rollladen has three l's because it comes from Roll- + Laden.

Nachts means at night or during the night.

It is a very common time adverb. You can think of it as a fixed expression.

Examples:

• nachts = at night
• tagsüber = during the day
• morgens = in the morning

So der Rollladen nachts Lärm macht means the shutter makes noise at night.

Yes. Lärm machen literally means to make noise.

This is a normal German expression:

• Lärm machen = to make noise
• viel Lärm machen = to make a lot of noise

So Wenn der Rollladen nachts Lärm macht is a very natural way to say that the shutter is noisy or makes noise at night.

Schließe is the ich form of the verb schließen.

Conjugation:

• ich schließe
• du schließt
• er/sie/es schließt
• wir schließen

The ß appears in forms based on the stem vowel pattern of schließen.

A useful point:

• schließen = to close
• ich schließe = I close / I am closing

In Switzerland, you may see ss instead of ß, but standard German in Germany and Austria uses ß here.

Because it is the direct object of schließen.

You are closing what?

• das Fenster

So it must be in the accusative case. For das, nominative and accusative look the same:

• nominative: das Fenster
• accusative: das Fenster

That is why the form does not change visibly here.

Here ganz means completely or all the way.

So:

• das Fenster ganz schließen = to close the window completely

It does not mean whole here. It is being used as an adverb.

Compare:

• Ich schließe das Fenster. = I close the window.
• Ich schließe das Fenster ganz. = I close the window completely.

Yes, that would also be natural in everyday German.

Compare:

• Ich schließe das Fenster ganz.
• Ich mache das Fenster ganz zu.

Both mean that you close the window fully.
However:

• schließen is a bit more neutral and standard
• zumachen or zu machen can sound a bit more conversational

So the sentence you were given is perfectly normal.

Because in German, a subordinate clause introduced by wenn must be separated from the main clause by a comma.

So:

• Wenn der Rollladen nachts Lärm macht, schließe ich das Fenster ganz.

This comma is required in standard German spelling.

Yes. You can also put the main clause first:

• Ich schließe das Fenster ganz, wenn der Rollladen nachts Lärm macht.

The meaning stays basically the same.

The difference is mainly in focus and rhythm:

• starting with Wenn ... emphasizes the condition/situation first
• starting with Ich schließe ... emphasizes the action first