Hun sier at hver arbeidstaker trenger god opplæring, ellers blir den nye jobben vanskelig.

Because sier is the present tense of the verb å si (to say).

• å si = to say
• sier = says / is saying
• sa = said
• har sagt = has said

So Hun sier means She says.

At means that and introduces a subordinate clause.

So:

• Hun sier = She says
• at hver arbeidstaker trenger god opplæring = that every worker needs good training

In English, that is often optional:

• She says every worker needs good training
• She says that every worker needs good training

In Norwegian, at is very commonly used in this kind of sentence.

Hver arbeidstaker means each worker or every worker, while alle arbeidstakere means all workers.

They are similar, but the grammar is different:

• hver arbeidstaker = singular form after hver
• alle arbeidstakere = plural form after alle

So:

• hver arbeidstaker trenger = each worker needs
• alle arbeidstakere trenger = all workers need

Because hver is singular, the noun stays singular too: arbeidstaker, not arbeidstakere.

Because the subject is hver arbeidstaker, which is grammatically singular.

Even though hver arbeidstaker refers to many people in a general sense, Norwegian treats hver + singular noun as singular.

So:

• Hver arbeidstaker trenger ... = Each worker needs ...
• not Hver arbeidstaker trenger ikke / trenger? Actually the important point is that the verb stays singular-looking in Norwegian.

A useful comparison:

• Hver student leser boken. = Each student reads the book.
• Alle studenter leser boken. = All students read the book.

In the present tense, Norwegian verbs do not change much by person, but the subject is still grammatically singular.

Arbeidstaker usually means employee, worker, or member of the workforce.

It is a fairly standard and slightly formal word. In many contexts, employee is the best translation.

Compare:

• arbeidstaker = employee / worker
• arbeider = worker, often more specifically a laborer or working person
• ansatt = employee

So in this sentence, arbeidstaker sounds general and somewhat formal.

Here opplæring is being used in a general, uncountable sense: good training.

That is why Norwegian does not use the article en here.

• god opplæring = good training
• en god opplæring = a good training / a good course of training

The version with en is possible in some contexts, but it sounds more like one specific training program or training period.

In this sentence, the speaker means training in general, so god opplæring is the natural choice.

These words overlap a bit, but they are not the same:

• opplæring = training, instruction, teaching someone how to do a job or task
• utdanning = education
• trening = training in the sense of practice, exercise, or physical training, and sometimes skill training

In a work context, opplæring is often the best word for job training or instruction.

So:

• god opplæring = proper/good training for the job

Ellers here means otherwise.

It introduces the consequence if the first condition is not met:

• hver arbeidstaker trenger god opplæring = every worker needs good training
• ellers blir den nye jobben vanskelig = otherwise the new job becomes / will be difficult

So the structure is basically:

X is necessary, otherwise Y happens.

Because Norwegian follows the V2 rule in main clauses: the finite verb usually comes in the second position.

When ellers is placed first, the verb must come immediately after it:

• Ellers blir den nye jobben vanskelig.

This is called inversion.

Compare:

• Den nye jobben blir vanskelig.
• Ellers blir den nye jobben vanskelig.

The subject den nye jobben comes after the verb because ellers takes the first position.

This is very common in Norwegian:

• I dag kommer han. = Today he is coming.
• Da skjønte jeg det. = Then I understood it.
• Ellers blir jobben vanskelig. = Otherwise the job will be difficult.

This is because Norwegian normally uses double definiteness when a noun is definite and has an adjective.

• jobben = the job
• den nye jobben = the new job

You need both:

1. the definite article before the adjective: den
2. the noun in definite form: jobben

So:

• en ny jobb = a new job
• den nye jobben = the new job

Den nye jobb is not standard in ordinary modern Norwegian.

Yes, blir literally comes from å bli, which often means become. But in many contexts, especially like this one, it is very natural to translate it as will be or ends up being.

So:

• jobben blir vanskelig can mean the job becomes difficult
• but in context it often sounds more natural in English as the job will be difficult

The idea is that without good training, the result is that the new job turns out difficult.

Because at introduces a subordinate clause, while ellers blir ... is a main clause.

After at, Norwegian usually does not use the V2 pattern. The subject comes before the verb in a more regular way:

• at hver arbeidstaker trenger god opplæring

Here the order is:

• hver arbeidstaker = subject
• trenger = verb

But in the main clause:

• Ellers blir den nye jobben vanskelig

Here the V2 rule applies, so the verb comes second.

This contrast is very important in Norwegian:

• Hun sier at han kommer.
• I morgen kommer han.

First sentence: subordinate clause after at
Second sentence: main clause with a fronted expression

Grammatically, den nye jobben is definite, so it normally refers to a specific new job.

In context, though, Norwegian sometimes uses a definite phrase where English might be a little more flexible. Here it most naturally means the new job that the worker is starting.

If you wanted a more general meaning like a new job, you would normally say:

• en ny jobb

So the contrast is:

• en ny jobb = a new job
• den nye jobben = the new job

In this sentence, the definite form suggests a particular new job situation being discussed.