Vores chef ændrede dagsordenen meget sent, hvilket gjorde mødet længere end forventet.

Because after a possessive like min, din, vores, deres, Danish normally uses the indefinite form of the noun:

• vores chef = our boss
• not vores chefen

This works like English: we say our boss, not our the boss.

A few examples:

• min bil = my car
• deres hus = their house
• vores møde = our meeting

So chef stays indefinite here.

Vores means our.

It is the possessive form of vi (we). Unlike some other Danish words, vores does not change form depending on the gender or number of the noun:

• vores chef = our boss
• vores møde = our meeting
• vores planer = our plans

So it is a very stable word to learn.

Dagsordenen is the definite singular form of dagsorden.

• en dagsorden = an agenda
• dagsordenen = the agenda

In this sentence, it is a specific agenda, probably the one for that meeting, so Danish uses the definite form.

The noun is common gender (en-word), so the definite ending is -en:

• en chef → chefen
• en dagsorden → dagsordenen

Ændrede is the past tense of ændre, which means to change.

• at ændre = to change
• ændrer = changes / is changing
• ændrede = changed
• har ændret = has changed

So:

• Vores chef ændrede dagsordenen = Our boss changed the agenda

This is a very common Danish past-tense pattern: many verbs form the past with -ede or -de.

Meget sent literally means very late.

• sent = late
• meget = very

So:

• ændrede dagsordenen meget sent = changed the agenda very late

This is natural Danish word order. The phrase meget sent acts as an adverbial phrase describing when/how late the action happened.

Also note the order:

• meget sent = very late
• not sent meget

That is because meget modifies sent.

Here hvilket means something like which or which fact.

It refers to the whole previous clause, not just one noun.

So in:

• Vores chef ændrede dagsordenen meget sent, hvilket gjorde mødet længere end forventet.

hvilket refers to the entire idea of the boss changing the agenda very late.

In English, this is like:

• Our boss changed the agenda very late, which made the meeting longer than expected.

So hvilket is useful when you want to comment on an entire situation.

Because hvilket refers to the entire preceding statement, while som usually refers to a specific noun.

Compare:

• chefen, som ændrede dagsordenen
  = the boss, who changed the agenda

Here som refers to chefen.

But in your sentence:

• ..., hvilket gjorde mødet længere ...

Here the meaning is that whole thing made the meeting longer, so hvilket is the better choice.

A good rule of thumb:

• som → refers to a noun
• hvilket → refers to a whole clause or idea

Because hvilket gjorde mødet længere end forventet is a following clause that comments on the main clause.

In Danish, many writers place a comma before this kind of clause, especially in formal or teaching contexts. You will very often see:

• ..., hvilket ...

So the comma helps show that the second part explains the consequence of the first part.

This is a very common Danish structure:

• gøre + object + adjective

It means make + object + adjective in English.

So:

• gjorde mødet længere = made the meeting longer

Other examples:

• Det gjorde mig glad. = It made me happy.
• Regnen gjorde vejen glat. = The rain made the road slippery.

So gjorde here is not did in the simple sense; it is part of the pattern make something become X.

Længere is the comparative form of lang (long).

• lang = long
• længere = longer
• længst = longest

So:

• mødet længere = the meeting longer

This is an irregular-looking comparison, so it is worth memorizing.

Compare with English:

• long → longer
• Danish: lang → længere

Because end forventet is a natural shortened Danish expression meaning than expected.

Literally:

• end = than
• forventet = expected

A fuller version could be something like:

• end man havde forventet = than one had expected
• end forventet = than expected

So Danish often leaves out words that are understood from context. This makes the sentence more compact and natural.

Forventet is the past participle of forvente (to expect).

• at forvente = to expect
• forventer = expects / is expecting
• forventede = expected
• forventet = expected

In end forventet, it works like an adjective or reduced clause meaning than was expected.

So even though it looks short, it is grammatically very normal Danish.

The main structure is:

• Vores chef = subject
• ændrede = verb
• dagsordenen = object
• meget sent = adverbial
• hvilket gjorde mødet længere end forventet = clause showing the result

So the sentence is built like this:

Subject + verb + object + adverbial + result clause

That is very typical Danish.

A rough breakdown:

• Vores chef ændrede dagsordenen meget sent
• hvilket gjorde mødet længere end forventet

The second part explains the consequence of the first.