Wir reinigen den Trommelröster und das Kühlsieb.

Because wir means we, and the verb has to match that subject.

The infinitive is reinigen = to clean.
In the present tense, it changes like this:

• ich reinige = I clean
• du reinigst = you clean
• er/sie/es reinigt = he/she/it cleans
• wir reinigen = we clean
• ihr reinigt = you all clean
• sie/Sie reinigen = they clean / you (formal) clean

So wir reinigen is the correct form for we clean.

Because the two nouns have different grammatical genders:

• der Trommelröster is masculine
• das Kühlsieb is neuter

In this sentence, both nouns are direct objects, so they are in the accusative case.

That changes the articles like this:

• masculine: der → den
• neuter: das → das (no change)

So:

• den Trommelröster
• das Kühlsieb

Because Trommelröster is the object being cleaned, not the subject doing the action.

In German, the direct object usually takes the accusative case.
For masculine nouns, the article changes:

• nominative: der Trommelröster
• accusative: den Trommelröster

So in this sentence:

• Wir = subject
• reinigen = verb
• den Trommelröster = direct object

That is why den is required.

Yes. Both are classic German compound nouns, where smaller words are joined into one larger noun.

• Trommelröster = Trommel (drum) + Röster (roaster)
• Kühlsieb = Kühl- (cooling / cool-) + Sieb (sieve / screen)

A very useful rule in German is:

The last part of a compound usually determines the gender.

So:

• der Röster → der Trommelröster
• das Sieb → das Kühlsieb

That helps explain why one uses den and the other uses das in the sentence.

Because all nouns are capitalized in German.

So in this sentence:

• Wir is capitalized because it is the first word of the sentence.
• Trommelröster and Kühlsieb are capitalized because they are nouns.

This is one of the most visible differences between German and English spelling.

The sentence follows normal German main clause word order:

Wir | reinigen | den Trommelröster und das Kühlsieb.
subject | verb | objects

A key rule in German main clauses is:

The conjugated verb usually comes in second position.

Here:

• Wir = first position
• reinigen = second position
• den Trommelröster und das Kühlsieb = what comes after the verb

So this is a very standard, natural sentence pattern.

Und means and. Here it joins two direct objects:

• den Trommelröster
• das Kühlsieb

So the structure is basically:

We clean [the drum roaster] and [the cooling sieve].

Both items are things being cleaned.

Normally, no. In this sentence, you should keep both articles:

• den Trommelröster
• das Kühlsieb

That is especially important because the nouns have different genders and therefore different articles.

So the natural version is:

Wir reinigen den Trommelröster und das Kühlsieb.

Leaving out the second article would sound incomplete or ungrammatical here.

The articles show that clearly:

• den here is masculine singular accusative
• das here is neuter singular accusative

So both nouns are singular.

If they were plural, the articles and sometimes the nouns themselves might look different. For example, plural direct objects often use die.

All three can relate to cleaning, but they are used a bit differently:

• reinigen = to clean, often somewhat formal, technical, or process-focused
• putzen = to clean/polish, often more everyday speech
• säubern = to clean, purify, or clear; can sound more formal or specific depending on context

In a technical or workplace setting, reinigen is very natural.
So Wir reinigen den Trommelröster und das Kühlsieb sounds appropriate if this is an instruction, procedure, or work task.

Those vowel sounds do not exist in the same way in standard English, so they can feel tricky at first.

• ö in Trommelröster is a rounded front vowel.
  A common learner tip: say something like eh, but round your lips.

• ü in Kühlsieb is another rounded front vowel.
  A common learner tip: say ee, but round your lips.

Very roughly:

• Trommelröster sounds something like TROM-mel-RER-ster with a rounded vowel in the middle part
• Kühlsieb begins with a rounded ü sound

Also note:

• ie in Sieb is pronounced like a long ee
• ö and ü are separate letters in German, not just decorative versions of o and u

Because this is a main clause, not a subordinate clause.

In a normal main clause, German usually puts the conjugated verb in second position:

• Wir reinigen den Trommelröster und das Kühlsieb.

You may have seen verb-final order in sentences introduced by words like weil, dass, or wenn. For example:

• ..., weil wir den Trommelröster und das Kühlsieb reinigen.

So German does use verb-final order sometimes, but not in a simple standalone main clause like this one.

Sometimes yes, but compound nouns are often easier because the last element usually tells you the gender.

For these nouns:

• Röster is masculine → der Trommelröster
• Sieb is neuter → das Kühlsieb

So instead of memorizing the whole compound as a completely new mystery word, you can often work out the gender from the final part.

That is a very useful strategy when reading technical German vocabulary.