Vi skal sette opp en ny hylle i stuen i morgen.

Because skal is a modal verb, and in Norwegian, modal verbs are followed by the bare infinitive.

So you say:

• Vi skal sette opp ...
• Jeg kan hjelpe
• Hun må gå

Not:

• Vi skal å sette opp ... ❌

This is similar to English, where you say we will put up or we must go, not we will to put up.

Here, skal shows a planned future action: we are going to / we will.

In this sentence, it suggests that putting up the shelf is something already intended or arranged:

• Vi skal sette opp en ny hylle i stuen i morgen.

So it is not just a vague future. It often implies a plan, decision, or expectation.

Be aware that skal can also mean obligation in other contexts, like must or shall, depending on the sentence.

Because sette opp is a fixed verb expression, much like a phrasal verb in English.

• sette = to put, set
• sette opp = to put up, install, erect, set up

In this sentence, sette opp en ny hylle means put up/install a new shelf.

This is very common in Norwegian: a verb plus a small word like opp, ut, på, or av can create a more specific meaning.

Yes. In infinitive form, you often see it together:

• å sette opp
• skal sette opp

But in some sentence patterns, the particle opp can be separated from the verb, especially when other elements are inserted. For example:

• Vi setter opp hyllen i dag.
• Vi satte hyllen opp på veggen.
  This is possible, though often less natural in everyday speech than keeping the phrase close together.

In practice, learners will most often meet it as sette opp.

Because hylle is traditionally a feminine noun, but in Bokmål many feminine nouns can also be treated as masculine.

So both of these are possible in Bokmål:

• ei ny hylle
• en ny hylle

Both are correct.

This also affects the definite form:

• hylla / hylle in some contexts depending on style
• but most commonly for the definite singular: hylla or hyllen, depending on whether you use feminine or masculine patterns

Many learners use the common-gender-style en forms a lot in Bokmål, and that is completely normal.

Because the noun is singular and here treated as an en-word.

Adjective forms in Norwegian change depending on gender and number:

• en ny hylle
• et nytt bord
• nye hyller

So:

• ny = singular en-word
• nytt = singular et-word
• nye = plural and also definite noun phrases in many cases

Since hylle here is singular and used with en, ny is the correct form.

Stuen is the definite singular form of stue, meaning the living room.

• stue = living room
• stuen = the living room

So:

• i stuen = in the living room

In Bokmål, you may also see stua, especially if the noun is treated as feminine:

• i stua

Both stuen and stua can be correct, depending on style and gender choice.

Because i means in for location.

Here the sentence is talking about where the shelf will be put up:

• i stuen = in the living room

This is a normal location phrase.

In some contexts, Norwegian distinguishes between location and movement, but with rooms, i is very commonly used to mean in.

Yes, i morgen can move.

In the given sentence, it comes at the end because that is a very natural place for a time expression:

• Vi skal sette opp en ny hylle i stuen i morgen.

But Norwegian often allows time expressions in other positions too:

• I morgen skal vi sette opp en ny hylle i stuen.
• Vi skal i morgen sette opp en ny hylle i stuen.

The first alternative is especially common if you want to emphasize tomorrow.

So the meaning stays basically the same, but the focus can shift a little.

Yes. This is standard main-clause word order in Norwegian.

The pattern is:

• subject + finite verb + rest

So here:

• Vi = subject
• skal = finite verb
• sette opp en ny hylle i stuen i morgen = rest of the clause

This is very normal.

If you move something else to the front, Norwegian uses verb-second word order, meaning the finite verb still stays in second position:

• I morgen skal vi sette opp en ny hylle i stuen.

Notice that skal still comes second.

You usually put ikke after the finite verb:

• Vi skal ikke sette opp en ny hylle i stuen i morgen.

This means We are not going to put up a new shelf in the living room tomorrow.

That placement is very important. With a finite verb like skal, ikke normally comes after it in a main clause.

Not exactly.

Both can refer to the future, but they are not always interchangeable.

• skal often suggests a plan, arrangement, intention, or something expected to happen
• vil often means want to, and sometimes it can also refer to future meaning depending on context

So:

• Vi skal sette opp en ny hylle i stuen i morgen.
  = We are planning / going to put up a new shelf tomorrow.

If you say:

• Vi vil sette opp en ny hylle i stuen i morgen.

that more strongly suggests we want to put up a new shelf tomorrow.

So in this sentence, skal is the better choice if the action is planned.

Yes, but that would be a different form.

In your sentence, hylle is indefinite singular:

• en ny hylle = a new shelf

If you wanted the new shelf, you would use the definite form, and then you might see feminine or masculine patterns depending on style:

• den nye hylla
• den nye hyllen

So hylla is not interchangeable with hylle here, because it changes the meaning from a shelf to the shelf.