Tjenestereisen begynner i morgen.

Because Norwegian usually writes compound nouns as a single word.

• tjeneste = service, duty
• reise = trip, journey

So tjenestereise means business trip / work trip / official trip, and the definite form becomes tjenestereisen.

This is different from English, where similar expressions are often written as two words, such as business trip.

The ending -en is the definite singular ending here. It works like the in English.

• en tjenestereise = a business trip
• tjenestereisen = the business trip

So instead of using a separate word for the, Norwegian often adds the definiteness to the end of the noun.

It is normally treated as a noun based on reise, which is often feminine, but in Bokmål many feminine nouns can also be used with common-gender forms.

So you may see:

• en tjenestereise / tjenestereisen
• also possibly ei tjenestereise / tjenestereisa

For many learners, it is safest to recognize that tjenestereisen is a perfectly normal Bokmål form, even if the base noun can also be feminine.

A useful rule: in compounds, the last part usually determines the gender.

Because Norwegian often uses the present tense for future events, especially when the event is planned or scheduled.

So:

• Tjenestereisen begynner i morgen.

is completely normal, just like English can say:

• The trip starts tomorrow.

You do not need a special future form here.

No. Norwegian verbs do not change for person the way English verbs sometimes do.

For example:

• Jeg begynner = I begin
• Du begynner = you begin
• Han begynner = he begins
• Vi begynner = we begin

The verb form stays begynner in the present tense.

That makes Norwegian verb conjugation simpler than English in this area.

I morgen is a time expression meaning tomorrow.

It tells you when the trip begins.

In this sentence:

• Tjenestereisen = subject
• begynner = verb
• i morgen = time phrase

So the structure is basically:

• The business trip
  • starts
    • tomorrow

In modern Norwegian, i morgen is normally written as two words.

It is a fixed expression:

• i = in
• morgen = morning

Historically it literally meant something like in the morning, but in modern usage it means tomorrow.

So learners should usually just memorize i morgen as the standard written form.

Yes. Norwegian follows the verb-second rule in main clauses.

So you can say:

• Tjenestereisen begynner i morgen.
• I morgen begynner tjenestereisen.

Notice what happens in the second version:

• the time phrase comes first
• the verb begynner must still stay in the second position
• the subject tjenestereisen moves after the verb

You would not normally say:

• I morgen tjenestereisen begynner

That sounds wrong in Norwegian.

It sounds a bit formal or official.

A native speaker might use it in written language, work-related contexts, or formal speech. In casual everyday conversation, people might also say things like:

• jobbreisen
• forretningsreisen
• or simply talk around it with a phrase meaning the trip for work

So the sentence is correct and natural, but it has a somewhat official tone.

A rough learner-friendly guide is:

• Tjenestereisen ≈ SHEN-uh-steh-rye-sen
• begynner ≈ beh-YUN-er
• i morgen ≈ ee MOR-en

A few pronunciation notes:

• tj in tjeneste is often pronounced like sh
• gy in begynner has a front rounded vowel that English does not really have
• the r in morgen may be light, and the ending may sound reduced in fast speech

The exact pronunciation depends somewhat on dialect, but those approximations are a good start.