Abends lasse ich den Rollladen unten, damit das Zimmer ruhig und dunkel bleibt.

Abends means in the evenings or in the evening, depending on context.

In this sentence, it usually suggests a habitual action: something the speaker does regularly in the evening.

A useful distinction:

• abends = in the evenings / in the evening in a general, repeated sense
• heute Abend = this evening / tonight
• am Abend = in the evening, often more neutral or descriptive

The -s in abends is part of a fixed adverbial form. German has several time expressions like this:

• morgens = in the morning
• mittags = at noon / around lunchtime
• nachmittags = in the afternoon
• abends = in the evening
• nachts = at night

Because German main clauses follow the verb-second rule.

That means the finite verb must be in the second position. If you put Abends first, then the verb lasse must come next, and the subject ich follows after it.

So:

• Ich lasse abends den Rollladen unten.
• Abends lasse ich den Rollladen unten.

Both are correct. The second version puts more emphasis on the time expression abends.

Here lassen means to leave or to keep something in a certain state.

So ich lasse den Rollladen unten means:

• I leave the roller shutter down
• I keep the roller shutter down

This is different from another common use of lassen, where it means to let or to have something done.

Compare:

• Ich lasse den Rollladen unten. = I leave the shutter down.
• Ich lasse ihn rein. = I let him in.
• Ich lasse mein Fahrrad reparieren. = I have my bicycle repaired.

So in your sentence, lassen is about keeping something as it is.

Because Rollladen is the direct object of lassen, so it is in the accusative case.

Rollladen is a masculine noun:

• nominative: der Rollladen
• accusative: den Rollladen

That is why the sentence has den Rollladen.

A Rollladen is a roller shutter: a solid or semi-solid outside shutter that can be pulled down over a window.

It is not quite the same as:

• Vorhang = curtain
• Jalousie = blind
• Rollo = roller blind

So den Rollladen unten lassen means keeping the external shutter down, often to block light and noise.

Unten describes the state or position: the shutter is down.

So den Rollladen unten lassen means to leave the shutter in the down position.

By contrast:

• herunterlassen
• runterlassen

focus more on the movement of bringing it down.

Compare:

• Ich lasse den Rollladen herunter. = I lower the shutter.
• Ich lasse den Rollladen unten. = I leave the shutter down.

So unten is used because the sentence is about the result/state, not the action of lowering it.

Damit introduces a purpose clause. It means so that or in order that.

So:

• ..., damit das Zimmer ruhig und dunkel bleibt = ..., so that the room stays quiet and dark

This tells you the reason/purpose for leaving the shutter down.

A very common pattern in German is:

• main clause + damit
  • subordinate clause

Example:

• Ich gehe früh schlafen, damit ich morgen fit bin. = I go to bed early so that I’m fit tomorrow.

Because damit introduces a subordinate clause, and in German subordinate clauses the conjugated verb usually goes to the end.

So:

• damit das Zimmer ruhig und dunkel bleibt

This is normal German word order for subordinate clauses.

Compare:

• Main clause: Das Zimmer bleibt ruhig und dunkel.
• Subordinate clause: ..., damit das Zimmer ruhig und dunkel bleibt.

Bleibt means stays or remains, while ist just means is.

So the sentence is not only describing the room’s condition; it is saying the speaker wants that condition to continue.

• Das Zimmer ist ruhig und dunkel. = The room is quiet and dark.
• Das Zimmer bleibt ruhig und dunkel. = The room stays/remains quiet and dark.

That makes bleibt the better choice here, because the purpose of leaving the shutter down is to keep the room that way.

Because they are predicate adjectives, not adjectives directly in front of a noun.

After verbs like:

• sein = to be
• werden = to become
• bleiben = to stay/remain

adjectives do not take endings.

So:

• das Zimmer bleibt ruhig
• das Zimmer bleibt dunkel

But if the adjective comes before a noun, then it does take an ending:

• ein ruhiges Zimmer
• ein dunkles Zimmer

That is the difference.

Usually abends suggests a general habit or something that happens regularly in the evening.

So this sentence most naturally means: the speaker usually leaves the shutter down in the evening.

If you wanted to talk about one specific evening, German would more likely say something like:

• Heute Abend lasse ich den Rollladen unten. = This evening / tonight I’m leaving the shutter down.

So abends often gives the sentence a habitual feel.