Learn Hardcore Danish: Da hun ringede, var jeg på stationen og ventede. - When she called, I was at the station and waiting.

Past single event: Da hun ringede, var jeg på stationen. = When she called (that time) …
Habitual/future: Når hun ringer, tager jeg den. = Whenever she calls / When she calls (in general), I pick up.

Why is the word order var jeg and not jeg var in the main clause?

Danish main clauses follow the V2 rule: the finite verb must be in second position. The entire subordinate clause Da hun ringede sits in the first position, so the finite verb of the main clause (var) comes next, before the subject (jeg):

Correct: Da hun ringede, var jeg …
Incorrect: Da hun ringede, jeg var …

Then why is it hun ringede (subject before verb) in the da-clause?

Because subordinate clauses in Danish do NOT use V2. In subordinate clauses, the basic order is Subject–(adverbs like ikke)–Verb:

Da hun ringede …
With negation: Da hun ikke ringede … (adverb before the finite verb in a subordinate clause)

Why is there a comma after ringede?

You put a comma between a fronted subordinate clause and the following main clause:

Da hun ringede, var jeg på stationen … If you switch the order, you generally put a comma before the da-clause:
Jeg var på stationen og ventede, da hun ringede.

What tense are ringede and var, and could I use the perfect instead?

Both ringede and var are preterite (simple past). With da referring to a specific past point, Danish strongly prefers the preterite:

Natural: Da hun ringede, var jeg …
Not natural: Da hun har ringet, … If you need past-before-past, use pluperfect:
Da hun havde ringet, gik jeg afsted. = After she had called, I left.

How do you express the English past progressive (“was waiting”) in Danish? Is var ved at correct?

Danish typically uses the simple past or a periphrastic construction:

Simple past: Jeg ventede.
With posture verbs for ongoing action: Jeg stod/sad og ventede.
Coordination (as in the sentence): Jeg var på stationen og ventede. Avoid var ved at vente here; være ved at + infinitive means “be about to,” not a general progressive.

Do I need to repeat the subject after og? Why not … var jeg på stationen og jeg ventede?

No repetition is needed when coordinating predicates with the same subject. Danish naturally shares the subject:

Natural: … var jeg på stationen og ventede.
Acceptable but clunky: … var jeg på stationen, og jeg ventede. (use this only for emphasis, contrast, or a deliberate rhythmic effect)

Why på stationen and not i stationen or ved stationen?

på stationen = at the station (default, institution/location as a whole; inside or on the premises)
i stationen = inside the station building (emphasizes interior)
ved stationen = by/near the station (outside, in the vicinity) All three can be correct, depending on the nuance you want.

Why is it the definite form stationen and not en station?

Danish marks definiteness with a suffix. Stationen = the station (a specific one presumed known from context). Use the indefinite if it’s non-specific:

Specific: Jeg var på stationen.
Non-specific: Jeg var på en station.

Could I drop og ventede and just say I was at the station?

Yes. Da hun ringede, var jeg på stationen. simply states your location at that time. Adding og ventede adds the ongoing activity and gives a more vivid, progressive-like picture.

Can I reverse the order: Jeg var på stationen og ventede, da hun ringede?

Yes. That’s fully natural. Note the different word order in the main clause (no inversion because nothing has been fronted):

Fronted subclause: Da hun ringede, var jeg …
Main clause first: Jeg var … , da hun ringede.

Where does negation ikke go in a sentence like this?

In the main clause after inversion: Da hun ringede, var jeg ikke på stationen.
In a subordinate clause before the finite verb: Da hun ikke ringede, var jeg på stationen. General rule: main clause = Verb (2nd) … ikke; subordinate clause = Subject … ikke … Verb.

Can I say Da ringede hun instead of Da hun ringede?

Yes, but it means something different:

Da hun ringede … = When she called (subordinator da
- subclause; time of the event)
Da ringede hun. = Then she called (adverb da = “then,” followed by V2 word order in a main clause). This is a narrative “then …” rather than a “when …” clause.

How do I say “She called me” or “I was waiting for her” correctly?

Telephone “call” takes a preposition: Hun ringede til mig. Not ringede mig (unless you use the particle verb) → Hun ringede mig op.
“Wait for” is vente på: Jeg ventede på hende. Not ventede for hende.