Efter regnet fick de dörren målad igen.

Because regnet is the definite form: the rain. In this sentence, it refers to a specific rain event that both speaker and listener can identify from the situation.

So Efter regnet means after the rain / after it had rained.

Using efter regn would sound much more general, like after rain in a broad or abstract sense, and is not the natural choice here.

This is because Swedish main clauses follow the V2 rule: the finite verb must come in the second position.

Here, Efter regnet is placed first. That means the verb fick must come next, before the subject de.

So:

• Efter regnet fick de dörren målad igen. = correct
• Efter regnet de fick dörren målad igen. = incorrect

A more basic word order would be:

• De fick dörren målad igen efter regnet.

Here fick is the past tense of få, but it does not simply mean got in the sense of receiving something.

In this kind of sentence, få often means something like:

• get something done
• have something done
• manage to get something done

So fick de dörren målad means they got the door painted / had the door painted.

It does not mean they literally received a painted door.

The structure is:

• de = subject
• fick = finite verb
• dörren = object
• målad = complement describing the object

So målad tells you the resulting state of dörren: the door ended up painted.

This is a common Swedish pattern:

• få + object + past participle/adjective

Examples:

• Hon fick bilen lagad. = She got the car repaired.
• Vi fick huset sålt. = We got the house sold.

Because målad is a past participle used like an adjective, and it agrees with dörren.

Dörren is:

• an en-word
• singular
• definite

So the matching form is målad.

Compare:

• en dörr → målad
• ett hus → målat
• dörrar → målade

So:

• dörren målad = correct
• dörren målat = wrong, because målat would match an ett-word
• dörren måla = wrong, because måla is the infinitive

Not necessarily.

This construction usually means that they arranged for it to be done, or they succeeded in getting it done. The sentence does not say who actually did the painting.

So de could be:

• the people who hired a painter
• the people responsible for the work
• the people who managed to get the job done

If you specifically wanted to say that they themselves did the painting, you would usually say something more direct, like:

• De målade dörren igen efter regnet.

Igen means again, and here it goes with the idea of the door being painted.

So the sense is:

• the door was painted again
• the door was repainted

In other words, the painting happened one more time.

Its position after målad is natural in Swedish:

• fick dörren målad igen

Yes, very much.

A good English parallel is:

• They had the door painted again after the rain.

Swedish often uses få + object + participle where English may use either:

• get something done
• have something done

So this sentence is very close in structure and meaning to that English pattern.

Yes. In everyday spoken Swedish, de is very often pronounced dom.

So although it is written de, many speakers would say something like:

• Efter regnet fick dom dörren målad igen.

This is normal in speech. In standard writing, de is still the usual spelling.

Because the sentence is focusing on what they got done, not just on the event itself.

Compare:

• Efter regnet fick de dörren målad igen.
  Focus: they got the result achieved.

• Dörren målades igen efter regnet.
  Focus: the door was painted again.

Both can describe a similar situation, but the first one highlights the people who arranged or obtained the result.

Yes. Depending on context, fick can carry a slight sense of managed to, succeeded in, or were able to get.

So the sentence can suggest not only that the door ended up painted again, but also that they got that result accomplished.

That nuance is one reason få is common in this construction.