Hej, det var længe siden! Hvordan går det?

In both cases, det is basically it, but it is not referring to one specific thing.

• In Det var længe siden, det is a dummy subject: It had been a long time.
• In Hvordan går det?, det means something like it / things / everything: How is it going?

So a very literal translation sounds a bit odd in English, but the Danish is completely natural.

Danish often uses var here when you meet someone again after a long time. The idea is roughly:

• It has been a long time
• or Wow, it’s been ages

Even though English often uses the present perfect, Danish can naturally use the simple past in this kind of reaction. It sounds very idiomatic.

Længe siden means a long time ago or a long time since.

In Det var længe siden!, the full idea is something like:

• It’s been a long time since we last saw each other
• It’s been ages

The part since we last met / talked is understood and does not need to be said.

Yes. Det er længe siden is also very common.

Very roughly:

• Det er længe siden = more neutral, straightforward
• Det var længe siden! = often sounds a bit more like an immediate reaction when seeing someone again

Both are natural, and learners will hear both.

Literally, it means How goes it?

Here, går comes from gå, which usually means to go or to walk, but in this expression it means to be going in the sense of how life or things are going.

So:

• Hvordan går det? = How’s it going?
• very natural everyday Danish

Because Danish main questions follow the usual verb-second pattern.

So after the question word hvordan, the finite verb comes next:

• Hvordan går det?

This is the normal Danish order for direct questions.

Hvordan det går can appear inside a longer sentence, for example:

• Jeg ved ikke, hvordan det går.
• I don’t know how it’s going.

So Hvordan går det? is a direct question, while hvordan det går is part of a statement.

Yes, Hej is friendly and informal-to-neutral. It is extremely common in everyday Danish.

In this sentence, the whole tone is casual and warm, especially because Det var længe siden! suggests you know the person already.

If you wanted to be more formal, you might use Goddag, but in modern spoken Danish Hej is used very widely.

A learner-friendly guide:

• længe: the æ is somewhat like the vowel in English cat, but not exactly the same. The word is roughly LEN-ge, though the final -e is weak.
• går: the å is a rounded vowel, somewhat like the vowel in British law or more, but again not identical.

Two important letters here are:

• æ = a front vowel not found exactly in English
• å = a rounded back vowel, also not exactly English

If you want to sound more natural, listening and repeating is especially important with these vowels.

They are close, but not exactly the same.

• Hvordan går det? = How’s it going?
  This asks generally about life, work, things in general.
• Hvordan har du det? = How are you feeling? / How are you?
  This can sound a bit more personal or emotional.

In a casual reunion like this, Hvordan går det? is very natural.

Some common answers are:

• Det går godt. = It’s going well.
• Det går fint. = It’s going fine.
• Meget godt. = Very well.
• Ikke så godt. = Not so well.
• Jo tak, godt. Hvad med dig? = Good, thanks. What about you?

A very common short answer is simply:

• Godt, tak.

Usually, you would say Det var længe siden! to someone you already know and have not seen for a while.

So the full sentence feels natural in situations like:

• meeting an old friend
• seeing a classmate after months or years
• running into a former coworker

It would be less natural with a complete stranger, because Det var længe siden! assumes previous contact.