Learn Hardcore Dutch: Na de wedstrijd is de stemming in de kleedkamer vrolijk. - After the match the mood in the locker room is cheerful.

“is” is the finite verb.
“Na de wedstrijd” is a time expression (an adverbial) moved to the front.
So the core structure is: (Na de wedstrijd) – is – de stemming in de kleedkamer – vrolijk.

You could also analyze “de stemming” as the subject, with “in de kleedkamer” as a prepositional phrase modifying “stemming”, but functionally the whole phrase “de stemming in de kleedkamer” is the subject noun phrase.

Why does the verb come before the subject after “Na de wedstrijd”?

Dutch is a V2 language in main clauses: the finite verb must be in second position.

Neutral word order: De stemming in de kleedkamer is vrolijk na de wedstrijd.
If you put a time expression first (Na de wedstrijd), the verb must still stay in second place:
- Na de wedstrijd is de stemming in de kleedkamer vrolijk.

So when something other than the subject (here: a time phrase) comes first, the subject and verb invert: Time – Verb – Subject – ….

Could I also say “De stemming in de kleedkamer is vrolijk na de wedstrijd”? Is that correct, and is there a difference?

Yes, that sentence is grammatically correct:

De stemming in de kleedkamer is vrolijk na de wedstrijd.

The meaning is the same, but the emphasis changes slightly:

Na de wedstrijd is de stemming in de kleedkamer vrolijk.
→ Slightly more focus on the time (“after the match”).
De stemming in de kleedkamer is vrolijk na de wedstrijd.
→ Slightly more neutral; the focus is more on the state of the atmosphere.

Both are natural; the original version just foregrounds the time frame.

Why is it “de stemming” and not “het stemming”?

Because “stemming” is a de-word in Dutch.

You simply have to learn the grammatical gender of nouns:

de stemming (feminine → uses de)
de kleedkamer
de wedstrijd

All three nouns in this sentence are de-words, so you use de, not het. There is no rule that would make stemming a het-word here; it’s just lexical gender.

What exactly does “stemming” mean here? How is it different from “sfeer”?

Both stemming and sfeer can mean “atmosphere / mood”, but they have slightly different flavors:

stemming usually refers more to the emotional mood of people:
- De stemming is goed/slecht/vrolijk/gespannen.
  → “The mood is good/bad/cheerful/tense.”
sfeer is more about the overall atmosphere or vibe, which can include surroundings as well:
- De sfeer in het stadion is fantastisch.
  → “The atmosphere in the stadium is fantastic.”

In your sentence, stemming focuses on how people in the dressing room feel emotionally after the match.

Why is the adjective “vrolijk” at the very end of the sentence?

Because in a simple main clause with a linking verb like “zijn” (to be), the typical order is:

Subject – verb – (other information) – predicative adjective

Here:

Subject: de stemming in de kleedkamer
Verb: is
Time phrase: Na de wedstrijd (moved to the front)
Predicative adjective: vrolijk

With fronting, the structure becomes:

Na de wedstrijd – is – de stemming in de kleedkamer – vrolijk.

The adjective “vrolijk” describes the subject and naturally appears at the end of this main clause.

What is the nuance of “vrolijk” compared to words like “blij” or “gezellig”?

vrolijk = cheerful, jolly, in a good mood.
→ Often about general cheerfulness or lively good spirits.
blij = glad, happy (about something specific).
→ More about a feeling of happiness, e.g. Ik ben blij dat we gewonnen hebben.
gezellig = cozy, pleasant, sociable.
→ Not directly “cheerful mood” but the pleasant, cozy, friendly vibe of a situation or place.

In this sentence, “vrolijk” suggests that people are cheerful and in high spirits after the match.

Why is the verb in the present tense (“is”) when we’re talking about “after the match”? Shouldn’t it be past (“was”)?

Both are possible, depending on what you mean:

Na de wedstrijd is de stemming in de kleedkamer vrolijk.
→ Describes what typically / generally happens after matches, or a current situation you’re describing as if it’s happening now.
Na de wedstrijd was de stemming in de kleedkamer vrolijk.
→ Clearly refers to one specific past situation.

So:

is = present tense, can describe a current or habitual situation.
was = simple past, clearly a completed event.

Why do we use “in de kleedkamer” and not another preposition like “bij” or “op”?

Because “in” is the normal preposition to indicate inside a room or enclosed space:

in de kleedkamer = inside the dressing room.
bij de kleedkamer would mean near/by the dressing room, not inside.
op de kleedkamer would normally be strange; op is used for surfaces (“on”), not for being inside a room.

So “in de kleedkamer” is the natural choice to say “in the dressing room” in Dutch.

Can I also say “Na de wedstrijd is het in de kleedkamer vrolijk”? Is that correct and how does it differ?

Yes, that sentence is also correct:

Na de wedstrijd is het in de kleedkamer vrolijk.

Differences:

Original: Na de wedstrijd is de stemming in de kleedkamer vrolijk.
→ Explicitly mentions “de stemming” (the mood).
Alternative: Na de wedstrijd is het in de kleedkamer vrolijk.
→ Uses “het” as a dummy subject; the real focus is on the place:
- “After the match, it is cheerful in the dressing room.”

Both are natural. The original is a bit more formal/explicit; the version with “het … in de kleedkamer” is very idiomatic in spoken Dutch.