Noen prøver å rane sjåføren.

It can mean either one.

In Norwegian, noen can refer to:

• someone
• some people

So Noen prøver å rane sjåføren can mean:

• Someone is trying to rob the driver
• Some people are trying to rob the driver

The verb form prøver is the same for singular and plural, so the sentence itself does not tell you which one is meant. You need context.

Å is the infinitive marker, like to in English.

So:

• prøver = tries / are trying
• å rane = to rob

Together, prøver å rane means tries to rob or are trying to rob.

This is a very common pattern in Norwegian:

• Han prøver å sove = He is trying to sleep
• Vi prøver å lære norsk = We are trying to learn Norwegian

So after prøve in this meaning, you normally use å + infinitive.

Because the Norwegian present tense often covers both the simple present and the present progressive.

So prøver can mean:

• tries
• is trying / are trying

In this sentence, English usually sounds more natural with is trying or are trying:

• Someone is trying to rob the driver
• Some people are trying to rob the driver

Norwegian does not usually need a separate form like English is trying.

Rane is the infinitive form of the verb, meaning to rob.

Its forms are:

• å rane = to rob
• raner = rob / robs / is robbing
• ranet = robbed / has robbed

In your sentence, it appears after å, so you get the infinitive:

• å rane

This is an important vocabulary point.

• å rane = to rob, usually by threat or force, and usually from a person or place
• å stjele = to steal, focusing on the thing taken

Examples:

• Han ranet banken = He robbed the bank
• Han stjal pengene = He stole the money

So:

• rane sjåføren = rob the driver
• not steal the driver

English makes the same distinction:

• rob a person/place
• steal an object

Because sjåføren is the definite form: the driver.

Norwegian nouns often add the definite article to the end of the noun:

• en sjåfør = a driver
• sjåføren = the driver

So in the sentence:

• rane sjåføren = rob the driver

This is very normal in Norwegian. Instead of putting a separate word before the noun, Norwegian often attaches the definiteness to the noun itself.

Because Norwegian nouns do not change form for subject vs. object the way English pronouns do.

Compare English:

• the driver saw me
• I saw the driver

The noun the driver stays the same in English too.

Norwegian works similarly with nouns:

• Sjåføren ser meg = The driver sees me
• Jeg ser sjåføren = I see the driver

Only some pronouns change form:

• jeg / meg
• han / ham

But ordinary nouns like sjåføren stay the same.

No, this is normal Norwegian main-clause word order:

• Noen = subject
• prøver = finite verb
• å rane sjåføren = infinitive phrase

So the structure is basically:

Subject + verb + infinitive phrase

That is very common:

• Hun liker å lese = She likes to read
• De begynner å jobbe = They start to work / They start working
• Noen prøver å rane sjåføren = Someone / Some people are trying to rob the driver

A rough guide for an English speaker is:

shaw-FUR-en

A few notes:

• sj is usually like English sh
• å sounds somewhat like the vowel in law or more, depending on accent
• the stress is on the second part: -før-

So sjåfør is roughly shaw-FUR, and sjåføren adds -en:

• sjåføren = shaw-FUR-en

Exact pronunciation varies by dialect, but this rough version will help.

Yes, absolutely.

It is a normal, complete Norwegian sentence. It sounds like something you might hear in:

• a news report
• a crime story
• a description of a scene
• subtitles in a film

It is short and natural, and all the grammar is standard.

Yes, depending on style and meaning.

Some alternatives are:

• Noen forsøker å rane sjåføren.
  More formal than prøver, but very similar: Someone is attempting to rob the driver.

• En person prøver å rane sjåføren.
  Clearly singular: One person is trying to rob the driver.

• Noen prøver å rane en sjåfør.
  This would mean a driver, not the driver.

So the original sentence is natural, but small changes can make the meaning more specific.