Si tenim temps dissabte, volem visitar la biblioteca i endreçar el pis després.

Catalan often leaves subject pronouns out because the verb ending already shows who the subject is.

• tenim = we have
• volem = we want

So nosaltres is not necessary. You could add it for emphasis, but normally Catalan prefers to omit it.

They are both 1st person plural present indicative forms:

• tenir → tenim = we have
• voler → volem = we want

That is why the whole sentence is understood as talking about we.

Because in Catalan, after si for a real future condition, you normally use the present tense, not the future.

So:

• Si tenim temps... = If we have time...

This works much like English If we have time, not If we will have time.

Yes. In Catalan, the present tense is often used for current plans, intentions, or scheduled future actions.

Here volem visitar... i endreçar... means something like we want / we’re planning to visit... and tidy up...

So the present tense can sound very natural even when the action will happen later.

Catalan often uses days of the week directly as time expressions, without a preposition.

So:

• dissabte = on Saturday

This is completely normal. English needs on, but Catalan usually does not here.

Yes. That is also possible.

Catalan has some flexibility with time expressions, so both of these are natural:

• Si tenim temps dissabte...
• Si dissabte tenim temps...

The original version sounds very natural and puts the focus first on having time, then adds Saturday.

Because voler is followed directly by an infinitive in Catalan.

So you say:

• volem visitar
• volem endreçar

There is no extra word between voler and the next verb.

Because they both depend on volem.

The structure is:

• volem visitar...
• volem endreçar...

But Catalan, like English, does not need to repeat volem the second time, so it becomes:

• volem visitar la biblioteca i endreçar el pis

That means we want to visit the library and tidy the flat.

Endreçar means to tidy up, put in order, straighten up.

El pis here means the flat / apartment.

So endreçar el pis means to tidy up the apartment or to straighten up the flat.

A learner should notice that pis is a very common Catalan word for flat/apartment, not just something related to the English word piss.

Not always, but very often in everyday Catalan it does mean flat/apartment.

Context matters. In this sentence, endreçar el pis clearly means tidy the apartment, not anything else.

Here després means afterwards / later and is being used on its own as an adverb.

So:

• després = afterwards

You use després de only when something comes after it:

• després de dinar = after lunch
• després de visitar la biblioteca = after visiting the library

But in the sentence you gave, després stands alone, so de is not needed.

In this sentence, it most naturally means that the tidying happens after the library visit.

So the sequence is understood as:

1. visit the library
2. tidy the apartment afterwards

Its position at the end makes that reading very natural.

Because the sentence begins with a conditional clause:

• Si tenim temps dissabte

When that kind of clause comes first, Catalan normally separates it from the main clause with a comma in writing.

So the comma helps show the structure:

• condition first
• main statement after

It can be a bit of both, but in context it most naturally expresses a plan or intention.

Volem + infinitive can mean:

• we want to...
• we intend to...
• we’re planning to...

So here it sounds like a real plan, but one that depends on having enough time.