Hvis konfettien ender på gulvet, fejer jeg den op efter festen.

Because -en is the Danish definite article added to the end of a common-gender noun.

• konfetti = confetti
• konfettien = the confetti

Danish usually puts the at the end of the noun instead of using a separate word in front.

For the same reason: -et is the definite ending for a neuter noun.

• gulv = floor
• gulvet = the floor

So på gulvet means on the floor.

This is a very important Danish word-order rule.

When a sentence begins with something other than the subject, the finite verb usually comes before the subject in the main clause. Here, the sentence starts with the if-clause:

• Hvis konfettien ender på gulvet, ...

So in the main clause, Danish uses inversion:

• fejer jeg den op efter festen

not:

• jeg fejer den op efter festen

This is the normal V2 word order pattern in Danish.

Ender på gulvet literally means ends up on the floor.

It does not necessarily focus on the action of falling itself. Instead, it focuses on the final result or location.

So:

• falder på gulvet = falls onto the floor
• ender på gulvet = ends up on the floor

In this sentence, ender på gulvet sounds natural because it emphasizes where the confetti finishes up.

Because konfetti is treated as a common-gender noun in Danish, so the pronoun referring back to it is den.

Danish uses:

• den for common-gender nouns
• det for neuter nouns

Since it is konfettien, not konfettiet, the matching pronoun is den.

Feje op means to sweep up.

It is a verb plus a particle:

• feje = to sweep
• op = up

In Danish, the particle often comes later in the sentence, especially in a main clause:

• Jeg fejer den op = I sweep it up

So fejer jeg den op means I sweep it up.

That is normal Danish word order with these verb-particle combinations.

Compare:

• Jeg fejer konfettien op
• Jeg fejer den op

The object often comes before the particle op, especially when the object is a short pronoun like den.

This is similar to English sweep it up, where it also comes between the verb and up.

It means after the party.

• efter = after
• festen = the party

Again, -en marks the definite form:

• fest = party
• festen = the party

So efter festen is simply a prepositional phrase telling you when the sweeping happens.

Because Danish usually expresses the by attaching it to the noun:

• gulvet = the floor
• festen = the party
• konfettien = the confetti

This is one of the biggest structural differences from English.

Yes, but the meaning changes slightly.

• hvis = if
• når = when

Use hvis if the situation is conditional or uncertain:

• If the confetti ends up on the floor...

Use når if you expect it to happen:

• When the confetti ends up on the floor...

So hvis is the better choice if the speaker is presenting it as a possibility rather than a certainty.

In this sentence, konfetti behaves like a mass noun, much like English confetti.

That means it is treated as one substance or collection rather than as separate countable pieces.

So:

• konfetti = confetti
• konfettien = the confetti

Even though confetti consists of many little pieces, Danish commonly treats it as a single uncountable noun here.

Yes. In standard Danish, a subordinate clause like this is separated from the main clause with a comma:

• Hvis konfettien ender på gulvet, fejer jeg den op efter festen.

So the comma helps show that the first part is the condition, and the second part is the main statement.