Mitt skrivbord är stökigt igen, så jag måste lägga pappren i ordning.

Because skrivbord is an ett-word in Swedish: ett skrivbord.

Possessive words change depending on the gender and number of the noun:

• min for common-gender singular (en-word)
• mitt for neuter singular (ett-word)
• mina for plural

So:

• min bok = my book
• mitt skrivbord = my desk
• mina papper = my papers

In Swedish, you normally do not use the definite ending together with a possessive.

So you say:

• mitt skrivbord = my desk

not:

• mitt skrivbordet

This is different from English, where my desk and the desk are separate ideas but do not affect the noun form. In Swedish, the possessive already makes the noun definite enough, so -et is not added.

Because the adjective agrees with the noun it describes.

Since skrivbord is an ett-word, the adjective takes the neuter form:

• ett skrivbord är stökigt
• ett rum är litet

Compare with an en-word:

• en lägenhet är stökig

So stökigt matches skrivbord.

Stökigt means messy, untidy, or cluttered.

In this sentence, it describes a desk that has papers or things lying around in a disorderly way. It is a very natural word for physical mess.

A close English idea would be:

• My desk is messy again

Igen means again.

So är stökigt igen means is messy again.

Its position here is very natural in Swedish. The speaker is saying that the desk has become messy one more time. English and Swedish are similar here:

• It is messy again
• Det är stökigt igen

Because så here means so, and it is linking two main clauses:

• Mitt skrivbord är stökigt igen
• så jag måste lägga pappren i ordning

After this kind of så, Swedish keeps normal main-clause word order:

• subject + verb
• jag måste

So this is correct:

• ..., så jag måste ...

A useful comparison:

• Därför måste jag ... = Therefore I must ...
• ..., så jag måste ... = ..., so I must ...

With därför at the start, the verb comes second, so the subject follows it. But with coordinating så, jag måste stays normal.

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

So:

• jag måste lägga = I must put/arrange
• jag kan läsa = I can read
• jag vill gå = I want to go

Not:

• jag måste att lägga

This is similar to English, where we say must put, not must to put.

It means to put the papers in order, arrange the papers, or sort the papers out.

This is not just about physically placing them somewhere. It often suggests organizing them so they are neat or properly sorted.

So the idea is:

• the desk is messy
• the papers need to be organized

Lägga often means to lay or to put something down, especially something that is placed flat.

Since papper means paper(s), lägga is a very natural choice.

In this sentence, though, lägga ... i ordning works almost like a set expression meaning arrange or put in order.

You could also hear other ways to express a similar idea, such as:

• ordna pappren = organize the papers
• sortera pappren = sort the papers

But lägga pappren i ordning is perfectly understandable and natural.

Pappren is the definite plural form of papper.

The forms are:

• ett papper = a paper
• papper = papers
• papperen / pappren = the papers

So in the sentence, pappren means the papers.

It refers to specific papers that are understood from the situation — most likely the papers on the desk.

Yes. Pappren and papperen mean the same thing: the papers.

Pappren is a very common shortened form of papperen. Both are correct. Learners often notice this because it looks irregular, but it is normal Swedish.

So:

• papperen = the papers
• pappren = the papers

Same meaning, just different forms of the definite plural that you will both encounter.

Because i ordning is the fixed expression here.

I ordning often means:

• in order
• tidy
• organized
• ready

So lägga pappren i ordning means put the papers in order.

Swedish also has expressions with på, but they are different, for example:

• få ordning på något = get something under control / get something organized

So the preposition depends on the expression. In this sentence, i ordning is the right choice.