Det var først da vi talte om ordklasserne igen, at nutid og datid begyndte at give mere mening.

This is a very common Danish pattern meaning:

It was only when ..., that ... or It wasn’t until ..., that ...

So:

Det var først da vi talte om ordklasserne igen, at nutid og datid begyndte at give mere mening.

means roughly:

It was only when we talked about the word classes again that present tense and past tense started to make more sense.

Here først does not mean first in the sense of first, then, next. In this structure, it means only then / not until then.

They have different jobs.

• da introduces the time clause: when
• at introduces the result/main part of this det var ... at ... structure

So the sentence is built like this:

• Det var først da ...
• at ...

Literally:

• It was only when ...
• that ...

This is similar to English sentences like:

• It was only when we spoke again that it made sense.

In Danish, this pattern often uses both da and at.

Yes, først often means first, but in this sentence it means something closer to:

• only then
• not until then

So:

• Det var først da ... = It was only when ...
• først da = not until / only when

Examples:

• Det var først i går, jeg forstod det.
  It was only yesterday that I understood it.
• Jeg kom først hjem klokken ti.
  I didn’t get home until ten.

So here først is about delay in understanding, not about sequence.

Talte is the past tense of at tale (to speak / to talk).

• tale = infinitive
• taler = present
• talte = past

It is past because the sentence describes a past moment when something started making more sense.

• da vi talte om ordklasserne igen
  = when we talked about the word classes again

The whole sentence looks back on that moment from the past.

Ordklasse means word class or part of speech.

Examples of word classes are:

• nouns
• verbs
• adjectives
• pronouns

ordklasserne = the word classes

The ending -ne is the definite plural ending in Danish.

So:

• en ordklasse = a word class
• ordklasser = word classes
• ordklasserne = the word classes

In this sentence, it refers to specific word classes already known in context.

They are Danish grammar terms.

• nutid = present tense
• datid = past tense (often specifically the simple past / preterite)

So the sentence is about understanding verb tenses better.

A learner might also see:

• førnutid = present perfect
• førdatid = past perfect
• fremtid = future

In this sentence, nutid og datid are used as grammatical categories, so English would naturally translate them as the present tense and the past tense.

Danish often leaves out the article with abstract grammatical labels or school-subject terms when speaking generally.

So:

• nutid og datid
  literally: present tense and past tense

In English, we often prefer:

• the present tense and the past tense or just
• present and past tense

Danish can sound more natural without articles in this kind of context.

Igen means again.

Here it goes with talte om ordklasserne:

• vi talte om ordklasserne igen
• we talked about the word classes again

So the idea is that this was not the first time they discussed them.

Its position is normal in Danish. Danish adverbs like igen often come later in the clause than an English speaker might first expect.

This is a very natural Danish expression.

• begyndte = began / started
• at give mening = to make sense
• mere mening = more sense

So:

• begyndte at give mere mening
  = started to make more sense

The verb begynde is commonly followed by at + infinitive:

• begynde at forstå = begin to understand
• begynde at læse = begin to read
• begynde at give mening = begin to make sense

Both are possible, but they mean slightly different things.

• give mening = make sense
• give mere mening = make more sense

Here mere shows improvement: the learner already had some understanding, but now the tenses became clearer.

So the sentence suggests:

• they did not become perfectly clear all at once,
• but they started to seem more understandable than before.

The sentence uses an emphatic cleft structure to focus on the important moment.

Compare:

1. Det var først da vi talte om ordklasserne igen, at nutid og datid begyndte at give mere mening.
   = It was only when we talked about the word classes again that present and past tense started to make more sense.

2. Nutid og datid begyndte først at give mere mening, da vi talte om ordklasserne igen.
   = Present and past tense only started to make more sense when we talked about the word classes again.

Both are possible, but the original strongly highlights the moment when understanding changed.

Because Danish normally separates clauses with commas.

In this sentence, the part

• da vi talte om ordklasserne igen

is a subordinate clause, and it is followed by the next clause introduced by at.

So the comma helps show the structure clearly.

Danish comma usage is generally more systematic with subordinate clauses than English comma usage, so learners often notice more commas in Danish sentences.