Affaldsposen er fuld, når de henter affaldet og tømmer beholderen.

Because Danish usually writes compound nouns as a single word. Here you have:

affald + pose = affaldspose
affaldspose + -n / -en = affaldsposen

So affaldsposen means the garbage bag.

The s in the middle is a linking s, which is very common in Danish compounds. It does not usually change the meaning; it just helps form the compound naturally.

Danish usually adds the definite article to the end of the noun instead of putting a separate word like the in front.

So:

• affaldsposen = the garbage bag
• beholderen = the container / the bin
• affaldet = the garbage / the waste

The difference between -en and -et depends on grammatical gender:

• common gender nouns usually take -en
• neuter nouns usually take -et

So pose and beholder are common gender, while affald is neuter.

Here når means when.

In Danish, når is commonly used for:

• something that happens regularly or habitually
• something expected in the present or future

So this clause suggests a repeated or general situation: when they collect the garbage and empty the container.

A learner often compares this with da, which is more often used for a single event in the past.

Because når de henter affaldet og tømmer beholderen is a subordinate clause.

In Danish subordinate clauses, the subject normally comes before the finite verb:

• når de henter ...
• fordi han kommer ...
• hvis vi går ...

In main clauses, Danish usually has verb-second word order, but subordinate clauses do not follow that same pattern.

So når de henter is the normal and correct order.

De means they.

In this sentence, it most likely refers to the people who collect the garbage, such as sanitation workers or waste collectors. Danish often leaves this kind of subject general if the context makes it clear.

So de does not have to refer to a previously named group. It can simply mean the people who do this job.

Because the same subject, de, applies to both verbs.

So:

de henter affaldet og tømmer beholderen

means:

they collect the garbage and empty the container

Danish, like English, does not need to repeat the subject when two verbs are joined by og and have the same subject.

You could think of it as:

de henter affaldet, og de tømmer beholderen

but the repeated de is normally left out.

Because fuld agrees with affaldsposen, which is a singular common-gender noun.

In Danish, predicative adjectives also show agreement:

• en pose er fuld
• et glas er fuldt
• poserne er fulde

So here:

• affaldsposen is singular
• it is common gender
• therefore the correct form is fuld

Er fuld describes a state: the bag is full.

Bliver fuld would mean becomes full, which focuses on the change into that state.

So the sentence is describing the condition of the bag, not the process of filling up. That is why er fuld is the natural choice here.

Yes. Danish allows that.

You can also say:

Når de henter affaldet og tømmer beholderen, er affaldsposen fuld.

When the subordinate clause comes first, the main clause still follows normal Danish main-clause word order, so the finite verb comes before the subject:

• ..., er affaldsposen fuld
• not ..., affaldsposen er fuld

That is a very common Danish pattern.

Here affald works like an uncountable noun, similar to garbage, waste, or trash in English.

Even though it is uncountable, Danish can still use a definite form:

• affald = garbage / waste
• affaldet = the garbage / the waste

So de henter affaldet is perfectly normal Danish. It means they are collecting the garbage, not necessarily one specific countable item.