Learn Hardcore Polish: Przed ślubem on zawsze jest trochę nerwowy. - Before the wedding he is always a bit nervous.

In Polish, prepositions decide which case the noun must take.
The preposition przed (“before / in front of”) normally requires the instrumental case.

Nominative: ślub (a wedding)
Instrumental: ślubem

So after przed you have to use ślubem, not ślub. This is true both for the spatial meaning (“in front of the church” – przed kościołem) and the temporal meaning (“before the wedding” – przed ślubem).

Can we omit on in this sentence? When is on necessary?

Yes, you can omit on. The sentence

Przed ślubem zawsze jest trochę nerwowy.

is perfectly correct and very natural.

Polish is a “pro‑drop” language: subject pronouns (on, ona, oni etc.) are usually left out when the meaning is clear from context or verb form.
You keep on mainly when you want to emphasize or contrast:

Przed ślubem on zawsze jest trochę nerwowy, a ona jest zupełnie spokojna.
(Before the wedding, *he is always a bit nervous, and she is completely calm.*)

Why does the sentence start with Przed ślubem instead of On? Is that important?

Polish word order is relatively flexible, and it often likes to put time or place at the beginning of the sentence.

So:

Przed ślubem on zawsze jest trochę nerwowy.
On przed ślubem zawsze jest trochę nerwowy.

Both are correct. Starting with Przed ślubem just highlights the time frame (“as for the period before the wedding…”). Starting with On would put slightly more focus on the person (“as for him…”). The difference is mostly one of emphasis, not grammar.

Where can we put zawsze in this sentence? Are other word orders possible?

The most natural places for zawsze (“always”) here are:

Przed ślubem on zawsze jest trochę nerwowy.
On zawsze jest trochę nerwowy przed ślubem.
Zawsze przed ślubem on jest trochę nerwowy.

In general, zawsze tends to stand near the main verb, often after the subject:

On zawsze jest... / Ona zawsze bywa...

Forms like On jest zawsze trochę nerwowy przed ślubem are also possible, but sound slightly more formal or careful. Something like On jest trochę zawsze nerwowy would be odd; zawsze should not be split awkwardly from the verb/adjective it semantically goes with.

What exactly does trochę mean here? Is it “a little”, “a bit”, or “kind of”?

In this sentence trochę means “a bit / a little / somewhat” and it softens the adjective nerwowy.

jest nerwowy – he is nervous
jest trochę nerwowy – he is a bit nervous / a little nervous

It does not mean “kind of” in the vague English sense of “sorta” (though in casual speech it can feel similar). It literally expresses a small degree of nervousness.

Why is trochę before nerwowy, not before jest?

Trochę here works like a degree adverb/quantifier that modifies the adjective, not the verb:

trochę nerwowy = “a bit nervous” (modifies “nervous”)

So the natural pattern is:

jest trochę nerwowy (literally: “is a‑bit nervous”)

Putting trochę before jest (trochę jest nerwowy) is possible only in special contexts and sounds marked or contrastive. The neutral, default order is exactly as in the example.

Is nerwowy the same as “nervous”? Could we use zdenerwowany or zestresowany instead?

Nerwowy overlaps with English “nervous”, but has two main uses:

Temporary state:
- Jestem nerwowy przed egzaminem. – I’m nervous before the exam.
Character trait:
- On jest nerwowy. – He is a nervous / highly-strung / irritable person.

In your sentence it’s clearly the temporary state.

You can say:

Przed ślubem on zawsze jest trochę zdenerwowany.
Przed ślubem on zawsze jest trochę zestresowany.

Nuances:

zdenerwowany – “upset / worked up / on edge right now”
zestresowany – “stressed (because of pressure, responsibilities, organization, etc.)”

All three are possible; nerwowy is the most general and common here.

Why is the present tense jest used to talk about something that happens repeatedly?

Polish uses the present tense both for what is happening now and for regular or habitual actions, just like English:

On zawsze jest trochę nerwowy przed ślubem.
→ He is always a bit nervous before the wedding (whenever this situation occurs).

If you want to stress the repeated tendency, you can also use bywa:

Przed ślubem on zawsze bywa trochę nerwowy.
(literally “he always tends to be a bit nervous”.)

But jest is completely correct and natural for a habitual statement.

Should it be przed swoim ślubem to mean “before his wedding”?

You don’t have to add swoim here.

Przed ślubem on zawsze jest trochę nerwowy.
is normally understood from context as “Before his (own) wedding he is always a bit nervous.”, unless the context clearly points to someone else’s wedding.

You can add swoim for clarity or emphasis:

Przed swoim ślubem on zawsze jest trochę nerwowy.

This makes it very explicit that it’s his own wedding, but in many real conversations it would feel a bit heavy if the context is already clear.

Could we say Przed ślubem on zawsze się denerwuje instead of jest trochę nerwowy? What’s the difference?

Yes, you can; the meaning is close but not identical:

Przed ślubem on zawsze jest trochę nerwowy.
– Focus on his state: he is (in general) a bit nervous in that period.
Przed ślubem on zawsze się denerwuje.
– Focus on the process / action: he gets nervous / works himself up (he is in the act of becoming nervous, worrying, etc.).

So jest trochę nerwowy describes a condition, while się denerwuje describes what he does (he worries, gets agitated).

How would the sentence change if we talk about “she” instead of “he”?

You need to change both the pronoun and the adjective ending to match feminine gender:

Przed ślubem ona zawsze jest trochę nerwowa.
(Before the wedding she is always a bit nervous.)

Changes:

on → ona (he → she)
nerwowy → nerwowa (masculine → feminine form of the adjective)

How do you pronounce ślubem and nerwowy?

Approximate English-based guidance:

ślubem – roughly SHLOO-bem
- ś – like a soft “sh”, with the tongue closer to y in “she”
- ł – like English w in “we”
- stress is on the first syllable: ŚLU-bem
nerwowy – roughly ner-VOH-vy
- w – like English v
- stress is on the second syllable: ner‑WO‑vy

Polish stress is very regular: usually on the second‑to‑last syllable, as in both of these words.