Vi var venner dengang.

Because var is the past tense of at være (to be).

• er = am / is / are
• var = was / were

So:

• Vi er venner = We are friends
• Vi var venner = We were friends

English uses were with we, but Danish uses the same past form var for all persons.

Because it matches vi (we). If we are friends, the noun must be plural.

• en ven = a friend
• vennen = the friend
• venner = friends
• vennerne = the friends

So Vi var venner literally has friends, not friend.

In Danish, predicate nouns often appear without an article after to be, just as in English.

Compare:

• Vi var venner = We were friends
• Han er lærer = He is a teacher
• De er naboer = They are neighbors

You normally do not say Vi var nogle venner or Vi var de venner here. That would change the meaning.

Dengang means something like back then, at that time, or in those days, depending on context.

In this sentence, it gives a time background:

• Vi var venner dengang = We were friends back then

It often refers to a period already known from the conversation or story.

That is a very natural place for a time expression in Danish. Danish often puts adverbs like dengang near the end when the sentence is simple.

So this word order is completely normal:

• Vi var venner dengang.

You may also see other arrangements in broader contexts, but this version is the most straightforward and idiomatic here.

Yes. Dengang var vi venner is also correct.

The difference is mainly focus:

• Vi var venner dengang = neutral statement; back then is added at the end
• Dengang var vi venner = stronger emphasis on back then

This is a good example of normal Danish word order rules: when an element like dengang comes first, the finite verb comes next:

• Dengang
  • var
    • vi
      • venner

Yes, it is written as one word: dengang.

That is important, because Danish often combines elements into a single written word. Writing den gang would usually mean something different or sound unnatural in this sentence.

So here the correct form is:

• Vi var venner dengang.

A rough guide for English speakers:

• venner sounds a bit like VEN-uh
• dengang sounds roughly like DEN-gang with a soft, Danish-style ending

A few notes:

• v in Danish is usually like English v
• e in venner is shorter than many English learners expect
• the -er ending is often reduced, not pronounced like strong English air
• ng in dengang is like the ng in sing, not n-g separately

Exact pronunciation varies a bit by accent, but those rough approximations can help at first.

Usually yes. Venner normally means friends in the ordinary sense.

So Vi var venner dengang most naturally means We were friends back then.

If Danish wants to express a romantic relationship, it would usually use other wording, depending on the situation, such as:

• Vi var kærester = We were boyfriend and girlfriend / a couple

So venner does not normally imply a romantic relationship.

It is neutral and completely natural in both speech and writing.

It is:

• not especially formal
• not slangy
• not old-fashioned

You could use it in conversation, in a story, in a text message, or in ordinary written Danish.

Usually it refers to a past time or period, not just a single split second.

So in Vi var venner dengang, the listener normally understands:

• at that time
• in that period
• back then

It often contrasts with the present situation, suggesting that things may be different now.