Jeg skjønner ikke hele greia.

Skjønner is the present tense of å skjønne, which means to understand or to get.

In this sentence, Jeg skjønner ikke hele greia sounds a lot like:

• I don’t get the whole thing
• I don’t understand the whole thing

Compared with forstår:

• å forstå = a more neutral/basic to understand
• å skjønne = often a bit more everyday and conversational

So:

• Jeg forstår ikke hele greia = perfectly correct
• Jeg skjønner ikke hele greia = a little more informal/natural in casual speech

Because in a normal Norwegian main clause, the finite verb usually comes early in the sentence, and ikke normally comes after it.

So the pattern is:

• Jeg skjønner ikke ...
• literally: I understand not ...

This is standard Norwegian word order. English uses do not, but Norwegian does not need an extra helping verb here.

Compare:

• Jeg skjønner det. = I understand it.
• Jeg skjønner det ikke. = I don’t understand it.

Hele greia means the whole thing, the whole matter, or the whole deal.

• hele = whole, entire
• greia = the thing / the matter / the deal

So hele greia is a very common everyday way to refer to a situation, explanation, problem, or idea as the whole thing.

It is often a bit informal. It does not have to refer to a physical object; it can also refer to an abstract situation.

Because greia is the definite singular form: the thing / the matter.

The base form is:

• ei greie = a thing / a matter

The definite form is:

• greia = the thing / the matter

So:

• hele greia = the whole thing not
• hele greie = which would be incomplete/wrong here

In Bokmål, many feminine nouns can also appear with a masculine-style definite ending in some contexts, so you may sometimes see greien, but greia is very common and natural.

Because hele already works directly with the definite noun.

In Norwegian, hele + definite noun is a normal pattern:

• hele dagen = the whole day
• hele uka = the whole week
• hele huset = the whole house
• hele greia = the whole thing

You usually do not add den in this structure.

So hele greia is the natural form.

No, it is fairly informal and conversational.

Greie/greia is very common in everyday speech and writing, but it can sound casual. In more formal Norwegian, you might use words like:

• saken = the matter / the case
• situasjonen = the situation
• forholdet = the matter / circumstance
• poenget = the point

For example:

• Jeg forstår ikke hele saken = I don’t understand the whole matter/case
• Jeg skjønner ikke hele greia = I don’t get the whole thing

The second one sounds more relaxed and idiomatic in conversation.

Yes, very natural.

It sounds like something someone would say when:

• an explanation is confusing
• a situation does not make sense
• they understand part of something, but not all of it

It has a natural spoken feel, especially because of skjønner and greia.

Not necessarily.

Jeg skjønner ikke hele greia usually suggests:

• I don’t understand the whole thing
• I’m not getting the full picture
• I don’t really understand how all of this fits together

So it often implies partial understanding is possible. You may understand some parts, but not everything.

If you wanted to say you understand absolutely nothing, you might say:

• Jeg skjønner ingenting. = I understand nothing / I don’t get anything.
• Jeg forstår ingenting. = I understand nothing.

Skjønner is the present tense of å skjønne.

The forms are:

• å skjønne = to understand
• skjønner = understand / understands
• skjønte = understood
• har skjønt = have/has understood

So Jeg skjønner ikke hele greia literally has the present-tense verb form, just like English I don’t understand the whole thing.

A rough guide for an English speaker:

• skjønner sounds approximately like SHURN-er or SHYURN-er, but the vowel is not exactly like English
• greia sounds roughly like GRAY-a or GRY-a, depending on accent and how clearly it is pronounced

A few useful points:

• skj- in many varieties of Norwegian is pronounced like English sh
• ø is a rounded vowel that English does not really have
• -a at the end of greia is the definite ending

You do not need a perfect English approximation, but it helps to know that skjønner does not start with a hard sk sound like in skip.

Sometimes, yes, but the meaning shifts a little.

• Jeg skjønner ikke hele greia. = I don’t get the whole thing / the whole situation
• Jeg skjønner ikke alt. = I don’t understand everything

Hele greia sounds more like one connected matter or situation.
Alt is more general and means everything.

So they can overlap, but they are not always identical.

Yes, and that is also natural, but it means something slightly different.

• Jeg skjønner ikke greia. = I don’t get the point / I don’t get the whole deal / I don’t understand what this is about
• Jeg skjønner ikke hele greia. = I don’t understand the whole thing

Without hele, the sentence can sound even more idiomatic, almost like I don’t see what the big idea is or I don’t get what this is all about, depending on context.

So both are possible, but hele emphasizes the entirety of the matter.