Min veninde fortalte mig en hemmelighed, og jeg lovede ikke at sige den til nogen.

Veninde means female friend, while ven means male friend or sometimes just friend in a more general sense.

So:

• min ven = my male friend
• min veninde = my female friend

Since the speaker is referring to a female friend, veninde is used.

Danish possessives must agree with the gender/number of the noun being possessed.

• min is used with common gender nouns
• mit is used with neuter nouns
• mine is used with plural nouns

Veninde is a common gender noun, so you say:

• min veninde

Compare:

• min bog = my book
• mit hus = my house
• mine bøger = my books

Both are in the past tense.

• fortælle = to tell

• fortalte = told

• love = to promise
• lovede = promised

So the sentence describes two completed actions in the past:

1. the friend told the speaker a secret
2. the speaker promised not to tell it

A useful thing to notice is that many Danish past tense forms are quite simple and do not change for person:

• jeg fortalte
• du fortalte
• han fortalte

Unlike English, there is no change like I tell / she tells in the present, and in the past it stays the same for everyone too.

Because mig is the object form of jeg.

• jeg = I
• mig = me

In the sentence, the friend told me a secret, so Danish uses mig:

• Min veninde fortalte mig en hemmelighed

Compare:

• Jeg fortalte hende noget. = I told her something.
• Hun fortalte mig noget. = She told me something.

So this works just like I/me in English.

Because hemmelighed is a common gender noun, so its indefinite article is en.

• en hemmelighed = a secret
• hemmeligheden = the secret

This is also important later in the sentence, because when the noun is referred to again, it becomes den:

• en hemmelighed
• den = it

That agreement is normal in Danish:

• common gender noun → en, later den
• neuter noun → et, later det

Den refers back to en hemmelighed.

Since hemmelighed is a common gender noun, the correct pronoun is den.

So:

• en hemmelighed → den

If the noun were neuter, you would use det instead.

For example:

• et brev = a letter
• jeg læste det = I read it

In your sentence, den means it, referring specifically to the secret.

After a verb like love (to promise), the negation often comes before the infinitive phrase:

• jeg lovede ikke at sige den til nogen

This means:

• lovede = promised
• ikke at sige = not to say / not to tell

So the speaker promised not to tell it.

This placement is very natural in Danish. You can think of ikke as negating the infinitive action at sige.

Compare:

• Jeg prøvede ikke at grine. = I tried not to laugh.
• Hun besluttede ikke at gå. = She decided not to go.

Here, at is needed because sige is in the infinitive after lovede.

• love at gøre noget = to promise to do something
• love ikke at gøre noget = to promise not to do something

So:

• jeg lovede ikke at sige den til nogen

This is very similar to English to tell.

Danish sometimes leaves out at after certain modal verbs, such as:

• jeg kan sige det = I can say it
• jeg vil sige det = I want to say it / I will say it

But after love, you normally use at.

In Danish, sige noget til nogen is a very common pattern:

• sige noget til nogen = say something to someone
• fortælle noget til nogen can exist, but fortælle nogen noget is also very common

So:

• sige den til nogen = say it to anyone

Here the pronoun den is the thing being said, and til nogen tells you to whom.

A useful comparison:

• fortælle nogen noget = tell someone something
• sige noget til nogen = say something to someone

That is why the first clause is:

• fortalte mig en hemmelighed

but the second is:

• sige den til nogen

Both are natural, just with different verb patterns.

Because fortælle often takes an indirect object + direct object pattern:

• fortælle nogen noget = tell someone something

So:

• fortalte mig en hemmelighed = told me a secret

You can sometimes use a til phrase in Danish, but with fortælle, the pattern with the person directly after the verb is extremely common and usually the most natural.

So for learners, it is very helpful to remember:

• fortælle nogen noget
• sige noget til nogen

That difference explains a lot in this sentence.

Here nogen means anyone.

Because the sentence is negative:

• ikke ... til nogen = not ... to anyone

So:

• jeg lovede ikke at sige den til nogen = I promised not to tell anyone

This is a very common Danish pattern:

• Har du nogen venner her? = Do you have any friends here?
• Jeg kender ikke nogen her. = I don’t know anyone here.

In a negative sentence, nogen often corresponds to English anyone / anybody / anyone at all.

Both ideas exist in Danish, but they are used differently.

• ikke ... nogen = not ... anyone / not ... any
• ingen = no one / nobody / no / none

In your sentence, the structure is:

• jeg lovede ikke at sige den til nogen
• literally: I promised not to say it to anyone

That is a very natural way to say it.

You could also see ingen in other sentences, for example:

• Jeg sagde det til ingen. = I told no one.
• Ingen vidste det. = No one knew it.

For learners, ikke + nogen is often the easiest pattern to recognize.

No. After og connecting two main clauses, Danish normally keeps normal main-clause word order.

So you get:

• Min veninde fortalte mig en hemmelighed
• og jeg lovede ikke at sige den til nogen

In the second clause, jeg is the subject and lovede is the finite verb, which is completely normal.

You usually get inversion when something other than the subject comes first in a main clause, for example:

• I går fortalte min veninde mig en hemmelighed.

Here I går comes first, so the verb moves before the subject:

• I går fortalte min veninde ...

But after og, with jeg still first, there is no special inversion.

Yes, a few words may surprise English speakers:

• veninde
  Often sounds roughly like veh-NIN-de. The middle syllable is stressed.

• fortalte
  The r is Danish, not English, and the ending -te is usually light. You may hear something close to fo-TAL-de.

• hemmelighed
  This can be tricky because Danish often reduces unstressed syllables. The ending -hed is not pronounced like English head.

• lovede
  Often sounds smoother and less clearly separated than English speakers expect.

• nogen
  Often pronounced much more softly than its spelling suggests; many learners expect every consonant to sound clearly, but Danish frequently reduces sounds.

The biggest general tip: do not expect Danish pronunciation to match spelling closely. Listening to native audio is especially important with words like these.

Yes. Both can overlap with English tell, but they are not used in exactly the same way.

Very roughly:

• sige = say
• fortælle = tell

But in real Danish, the difference is often about the pattern:

• sige noget = say something

• sige noget til nogen = say something to someone

• fortælle noget = tell something / narrate something
• fortælle nogen noget = tell someone something

That is why the sentence uses:

• fortalte mig en hemmelighed
• sige den til nogen

This is a good example of how Danish verb patterns matter just as much as dictionary meanings.

Yes, absolutely. En hemmelighed is the normal word for a secret.

The expression:

• fortælle nogen en hemmelighed

is a very natural Danish equivalent of:

• tell someone a secret

And then:

• sige den til nogen

means tell it to anyone / say it to anyone, where it refers back to the secret.

So the sentence is very idiomatic Danish, not a strange word-for-word construction.