Hun lægger sine bøger i tasken, før hun går til universitetet.

Because Danish uses the reflexive possessive sin / sit / sine when the owner is the same as the subject of the clause.

Here, the subject is hun, and the books belong to her, so Danish says sine bøger = her own books.

• Hun lægger sine bøger i tasken = She puts her own books in the bag.
• Hun lægger hendes bøger i tasken would usually mean she puts another woman’s books in the bag.

Why sine specifically? Because bøger is plural, and the plural form of the reflexive possessive is sine.

They all mean his/her/its own, but they agree with the noun being owned, not with the person who owns it.

• sin = for a common-gender singular noun
• sit = for a neuter singular noun
• sine = for a plural noun

Examples:

• Hun tager sin taske. = She takes her own bag.
• Hun tager sit brev. = She takes her own letter.
• Hun tager sine bøger. = She takes her own books.

So in your sentence, bøger is plural, so sine is required.

This is a very common Danish learner question.

• lægger comes from at lægge = to lay, put, place
• ligger comes from at ligge = to lie, be lying, be located

So:

• Hun lægger sine bøger i tasken = She puts her books in the bag.
  This is an action.
• Bøgerne ligger i tasken = The books are in the bag / are lying in the bag.
  This is a state or position.

A simple way to remember it:

• lægge = movement/action
• ligge = position/result

Because tasken means the bag. In Danish, the definite article is usually attached to the end of the noun.

• taske = a bag
• tasken = the bag

So:

• i tasken = in the bag

If you wanted to say in a bag, you would say i en taske.

If you wanted in that bag, you would usually say i den taske.

In this sentence, tasken sounds natural because it refers to a specific, known bag, probably her own bag.

Because Danish often uses a bare plural noun when English might also use a bare plural.

• bøger = books
• sine bøger = her books / her own books

The possessive already makes the reference specific enough, so no article is needed.

Compare:

• bøger = books
• bøgerne = the books
• sine bøger = her own books

In this sentence, it effectively means into the bag, because the verb lægger already shows movement and placement.

Danish often uses i for both in and into, depending on context.

So:

• Hun lægger sine bøger i tasken = She puts her books into the bag.
• Bøgerne ligger i tasken = The books are in the bag.

If you want to make the movement extra explicit, Danish can sometimes use ind i, but it is not necessary here.

Because før hun går til universitetet is a subordinate clause.

Danish punctuation normally places a comma before subordinate clauses introduced by words like:

• at = that/to
• fordi = because
• hvis = if
• når = when
• før = before

So:

• Hun lægger sine bøger i tasken, før hun går til universitetet.

That comma is standard in Danish writing.

Because after a subordinating conjunction like før, Danish uses subordinate clause word order, where the subject usually comes before the finite verb.

So:

• før hun går = before she goes

This is normal subordinate-clause order:

• conjunction + subject + verb

Compare:

• Main clause: Hun går til universitetet.
• Subordinate clause: før hun går til universitetet

If the subordinate clause came first, the main clause would then show normal Danish inversion:

• Før hun går til universitetet, lægger hun sine bøger i tasken.

Notice that after the fronted subordinate clause, Danish puts the verb before the subject in the main clause:

• lægger hun not
• hun lægger

Not necessarily.

at gå til can literally mean to walk to, but in many contexts gå til universitetet simply means go to university or attend/go to the university.

So the exact nuance depends on context.

In your sentence, it will usually be understood as:

• she goes to the university
• she heads off to university

It does not strongly focus on the physical act of walking unless the context makes that important.

Because universitetet is the definite form: the university.

• et universitet = a university
• universitetet = the university

Danish often uses the definite form in places where English might say either the university or just university, depending on style and meaning.

So til universitetet literally looks like to the university.

Yes. Both verbs are in the present tense:

• lægger = puts
• går = goes

The sentence can describe:

1. something happening now, depending on context, or
2. a habitual action / routine

So it can mean something like:

• She puts her books in her bag before she goes to the university.
• She usually puts her books in her bag before going to university.

Danish present tense is often used for regular habits, just like English present simple.

It would become:

Før hun går til universitetet, lægger hun sine bøger i tasken.

The meaning stays the same, but the word order in the main clause changes.

Why? Because when a clause comes first in Danish, the finite verb in the main clause usually comes before the subject.

So:

• Normal order: Hun lægger ...
• After fronting: ..., lægger hun ...

This is a very important Danish word-order pattern.

A few words here are especially tricky for English speakers:

• lægger: the æ is a front vowel, somewhat like the vowel in English cat, but not exactly the same.
• går: the å sounds roughly like the vowel in English law for many learners.
• bøger: ø is a rounded front vowel that English does not really have.
• universitetet: long word, but the stress pattern becomes easier with practice.

The hardest part is often not just the vowels, but also that Danish pronunciation is usually softer and less clearly spelled-out than English learners expect.

In this sentence, no. Here it clearly refers back to the subject hun of the same clause.

That is exactly what reflexive possessives do in Danish: they point back to the subject of their own clause.

So in:

• Hun lægger sine bøger i tasken the books belong to her, the subject.

But learners should remember an important rule: reflexive possessives work within their own clause. If the clause structure changes, the reference can also change.