Hun kontrollerer planen grundig.

Because planen is the definite form of plan.

• en plan = a plan
• planen = the plan

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

So:

• Hun kontrollerer plan would sound incomplete or unnatural here
• Hun kontrollerer planen = She checks the plan

Kontrollerer is the present tense of å kontrollere.

• å kontrollere = to check / to inspect / to verify
• kontrollerer = checks / is checking

In Norwegian, the present tense is often made by adding -er to the infinitive stem:

• å snakke → snakker
• å jobbe → jobber
• å kontrollere → kontrollerer

So Hun kontrollerer planen grundig is a normal present-tense sentence.

Not always. This is an important false-friend type issue.

In this sentence, kontrollere usually means:

• check
• inspect
• review
• verify

It does not usually mean control in the sense of have power over.

So here, Hun kontrollerer planen grundig is more like:

• She checks the plan thoroughly
• She reviews the plan carefully

If you translate it as She controls the plan thoroughly, that would sound odd in English.

Because it describes how she checks the plan.

The sentence structure is:

• Hun = subject
• kontrollerer = verb
• planen = object
• grundig = adverbial description of manner

So the order is very natural:

• She checks the plan thoroughly
• Hun kontrollerer planen grundig

Norwegian often places this kind of word after the object in simple main clauses.

Here it functions like an adverb, because it describes the verb kontrollerer.

It tells us how she checks the plan: thoroughly.

But the interesting part is that in Norwegian, many words that look like adjectives can also be used adverbially without changing much.

Compare:

• en grundig kontroll = a thorough inspection
  Here grundig is an adjective describing a noun.
• Hun arbeider grundig = She works thoroughly
  Here grundig functions adverbially.

So in your sentence, grundig means thoroughly.

Because hun is the standard feminine subject pronoun in Bokmål.

• hun = she

You may also see ho in some dialects and in Nynorsk, but hun is the normal form in standard Bokmål.

So for a learner of Bokmål, Hun kontrollerer planen grundig is exactly what you would expect.

Yes. It follows the basic pattern:

Subject + Verb + Object + Adverbial

So:

• Hun = subject
• kontrollerer = verb
• planen = object
• grundig = adverbial

This is a very standard main-clause word order in Norwegian.

A learner should get used to this pattern because it appears constantly in simple statements.

Yes, that would also be natural.

• kontrollerer sounds a bit more formal or systematic
• sjekker is often more everyday and conversational

So both can work:

• Hun kontrollerer planen grundig = a bit more formal, like reviewing or inspecting
• Hun sjekker planen grundig = more everyday, like checking it carefully

The exact best choice depends on context.

Norwegian usually puts the definite article on the end of the noun.

So instead of:

• the plan

you get:

• planen

This ending -en is what makes the noun definite.

Roughly speaking:

• plan = a plan
• planen = the plan

This is one of the biggest structural differences from English, and it is completely normal in Norwegian.

Yes, often.

• grundig = thorough(ly)
• nøye = carefully

They are close, but not identical.

• grundig suggests doing something in a complete, thorough, detailed way
• nøye emphasizes care and attention

So:

• Hun kontrollerer planen grundig = She checks the plan thoroughly
• Hun kontrollerer planen nøye = She checks the plan carefully

Both are natural, but grundig has a stronger sense of thoroughness.

Yes. Norwegian present tense often covers both meanings.

So Hun kontrollerer planen grundig can mean:

• She checks the plan thoroughly
• She is checking the plan thoroughly

The exact meaning depends on context.

Unlike English, Norwegian usually does not need a special continuous form like is checking.