Garantiperioden begynner etter overtakelsen.

Because Norwegian commonly forms compound nouns as a single word.

• garanti = guarantee / warranty
• periode = period

Together, garantiperiode means warranty period or guarantee period, and the definite form is garantiperioden = the warranty period.

This is very normal in Norwegian. Where English often uses two words, Norwegian often uses one compound word.

The ending -en marks the noun as definite singular: the warranty period.

Compare:

• en garantiperiode = a warranty period
• garantiperioden = the warranty period

In Norwegian, the definite article is often attached to the end of the noun instead of appearing as a separate word like English the.

For the same reason: -en shows the definite singular form.

• en overtakelse = a takeover / handover / transfer / acceptance
• overtakelsen = the takeover / the handover / the acceptance

So both nouns in the sentence are definite:

• Garantiperioden = the warranty period
• overtakelsen = the handover / takeover

Begynner is the present tense of the verb å begynne = to begin.

Examples:

• å begynne = to begin
• begynner = begin / begins / is beginning, depending on context

In this sentence, it means begins.

Norwegian verbs do not change according to the subject the way English verbs do. So:

• jeg begynner = I begin
• du begynner = you begin
• den begynner = it begins
• de begynner = they begin

The form begynner stays the same.

Norwegian often uses the present tense for future meaning when the context is clear.

So Garantiperioden begynner etter overtakelsen can naturally mean:

• The warranty period begins after the handover
• or will begin after the handover

This is very common in Norwegian, just like English sometimes says things such as The meeting starts tomorrow.

Etter means after here.

Norwegian does not have a case system like German for ordinary nouns in this kind of sentence, so you do not need to worry about something like accusative or dative after etter.

You can just learn it as a preposition:

• etter møtet = after the meeting
• etter overtakelsen = after the handover

Overtakelse can mean different but related things depending on context, such as:

• takeover
• handover
• transfer
• acceptance of delivery / taking possession

In legal, construction, or contract contexts, overtakelsen often refers to the formal moment when something is handed over and accepted.

So the best English wording depends on the situation, even though the basic grammar is the same.

Because Norwegian usually expresses definiteness by adding an ending to the noun.

So instead of:

• the warranty period

Norwegian says:

• garantiperioden

And instead of:

• the handover

Norwegian says:

• overtakelsen

This is one of the most important differences from English noun structure.

No, this is the normal basic Norwegian word order for a main clause:

Subject + verb + adverbial

• Garantiperioden = subject
• begynner = verb
• etter overtakelsen = time expression / adverbial phrase

So the structure is very close to English:

• The warranty period begins after the handover.

Normally, no. Begynnes is a passive form and would not fit well in this sentence.

Natural:

• Garantiperioden begynner etter overtakelsen.

Unnatural or wrong for this meaning:

• Garantiperioden begynnes etter overtakelsen.

Use begynner when the period itself is what starts.

The dictionary forms are the indefinite singular forms:

• en garantiperiode
• en overtakelse

In dictionaries, Norwegian nouns are usually listed with their gender/article, so you would look them up under:

• garantiperiode
• overtakelse

The forms in the sentence are the definite versions:

• garantiperioden
• overtakelsen

A rough pronunciation guide for an English speaker could be:

• Garantiperioden ≈ guh-RAHN-tee-peh-ree-OH-den
• begynner ≈ beh-GIN-er
• etter ≈ ET-er
• overtakelsen ≈ OH-ver-tah-kehl-sen

A few useful notes:

• y in begynner is not like English y. It is a rounded vowel that many English speakers find difficult at first.
• The r sound varies by dialect.
• The g in garanti is a hard g.

This is only an approximation, but it can help as a starting point.

No, that would sound wrong in standard Norwegian.

You need either:

• En garantiperiode begynner etter en overtakelse = a warranty period begins after a handover
  or
• Garantiperioden begynner etter overtakelsen = the warranty period begins after the handover

Bare nouns without the article or definite ending usually do not work here.

Yes, it sounds somewhat formal or contract-related, mainly because of the nouns:

• garantiperioden
• overtakelsen

This kind of wording is common in:

• contracts
• construction documents
• warranty terms
• legal or administrative writing

But the grammar itself is completely normal Norwegian.