Vi bruger en frysepose til at opbevare brødet i fryseren, så det holder sig frisk længere.

Because Danish usually writes compound nouns as a single word.

• fryse
  • pose = frysepose
• literally, something like a freezing/freezer bag

This is very common in Danish. The last part is the main noun, and the first part describes it. So here the main noun is pose (bag), which is why the whole word behaves grammatically like pose.

This is about gender and definite form in Danish.

• pose is a common gender noun, so: en pose
• brød is a neuter noun, so: et brød
• fryser is a common gender noun, so: en fryser

When Danish makes a noun definite, it usually adds the article to the end:

• en fryser → fryseren = the freezer
• et brød → brødet = the bread

So:

• en frysepose = a freezer bag
• brødet = the bread
• fryseren = the freezer

Also, in a compound like frysepose, the gender comes from the last part, pose, so it takes en.

Because Danish often uses the definite form when talking about a specific thing already understood from the context.

Here, brødet means the bread we are talking about — the bread we want to store. English often says store bread, but Danish very naturally says opbevare brødet when it means the bread in question.

If you were speaking more generally about bread as a category, you might use brød instead.

For example:

• Brød kan opbevares i fryseren. = Bread can be stored in the freezer.
• Vi opbevarer brødet i fryseren. = We store the bread in the freezer.

Because bruge often works with til when you mean use something for / to do something.

The pattern is:

bruge + thing + til at + infinitive

So:

• Vi bruger en frysepose til at opbevare brødet
• literally: We use a freezer bag to store the bread

This is a very common structure in Danish.

Compare:

• Jeg bruger en kniv til at skære brød.
• Hun bruger sin telefon til at tage billeder.

Without til, the sentence would sound wrong or at least unnatural in this meaning.

Here så means so or so that.

It introduces the result:

• Vi bruger en frysepose ...
• så det holder sig frisk længere

So the idea is:

• we use a freezer bag,
• so that / with the result that the bread stays fresh longer.

Be careful: så can mean different things in other contexts, such as then, thus, or so in conversation. But in this sentence, it is a result connector.

Det refers back to brødet.

Since brød is a neuter noun, the pronoun is det:

• brødet → det

So det means it, referring to the bread.

The expression holde sig frisk means stay fresh or remain fresh. This is a reflexive expression, so it uses sig.

• holde by itself can mean hold or keep
• holde sig often means stay / remain

So:

• det holder sig frisk = it stays fresh

A useful contrast:

• Det holder brødet frisk. = It keeps the bread fresh.
• Brødet holder sig frisk. = The bread stays fresh.

That little sig changes the meaning.

Because længere is the comparative form used for duration.

• længe = for a long time / long
• længere = longer

In this sentence, the bread stays fresh for a greater amount of time, so Danish uses længere:

• holder sig frisk længere = stays fresh longer

Why not lang? Because lang is an adjective, used with nouns:

• en lang dag = a long day

But here we are talking about how long something stays fresh, so Danish uses the adverb form:

• længe
• længere

It literally means we use, but in Danish, just like in English, vi can also be used in a more general or instructional way.

So this sentence could mean:

• We use a freezer bag ... as a real statement about what we do
• or something closer to You use a freezer bag ... in an explanatory or instructional context
• or even One uses a freezer bag ... in a general sense

This kind of vi is very common in everyday Danish and often sounds more natural than a more formal impersonal phrasing.

Because i means in, and a freezer is understood as an enclosed space that things go inside.

So:

• i fryseren = in the freezer

This is the normal preposition here.

Also, fryseren is definite because it means the freezer — the one already known in the situation, such as the freezer in your kitchen or household.