Si estàs malalta, no has de treballar a l'oficina.

Si means if.

So Si estàs malalta... means If you are sick...

A very important point for English speakers: Catalan si means if, not yes.
Catalan yes is sí with an accent.

• si = if
• sí = yes

That accent changes the meaning.

Catalan has two verbs that can both translate as to be:

• ser
• estar

In this sentence, estàs comes from estar, because being sick is seen as a temporary condition or state.

• estàs malalta = you are sick

Using ets (from ser) would sound wrong here, because ser is usually used for identity, essential characteristics, origin, profession, and similar ideas.

Compare:

• Ets metgessa = You are a doctor
• Estàs malalta = You are sick

Malalt / malalta is an adjective meaning sick. It changes form to match the gender of the person being described.

• malalt = masculine singular
• malalta = feminine singular
• malalts = masculine plural
• malaltes = feminine plural

So this sentence is addressing a woman:

• Si estàs malalta... = If you are sick (said to a woman)

If you were speaking to a man, it would be:

• Si estàs malalt...

It is not written, because Catalan often leaves subject pronouns out when the verb already makes the person clear.

• estàs already means you are
• has already means you have

So Catalan does not need tu here.

You could say:

• Si tu estàs malalta, no has de treballar...

but normally tu is omitted unless you want emphasis or contrast.

Yes, has by itself means you have, from the verb haver.

But haver de + infinitive is a very common structure meaning:

• to have to
• must
• need to

So:

• has de treballar = you have to work / you must work

Because of the no, the sentence says:

• no has de treballar = you must not work / you shouldn’t work / you don’t have to work

Exactly how strong it sounds depends on context, but grammatically it is the haver de + infinitive pattern.

It is a normal and understandable structure, but learners should know that Catalan can express this idea in more than one way.

• No has de treballar can mean you must not work or sometimes you don’t have to work, depending on context.
• If you want a very clear sense of prohibition, Catalan often uses other expressions too, such as no pots treballar in some contexts, depending on the intended meaning.

In this sentence, the intended idea is clearly something like: if you are sick, working at the office is not what you should do.

So no has de treballar is perfectly natural here.

The basic form is treballar, which means to work.

After de, Catalan uses the infinitive:

• has de treballar = you have to work
• he de treballar = I have to work
• hem de treballar = we have to work

So treballar is not conjugated here because it comes after de in the haver de + infinitive structure.

This is made of:

• a = at / to / in
• la oficina = the office

But Catalan usually contracts a + la/el only in some cases? Here the key thing is that the noun begins with a vowel, so the article la becomes l':

• la oficina → l'oficina

So:

• a l'oficina = at the office / in the office

The apostrophe appears because oficina starts with o.

English speakers often expect one preposition to match in, at, or to, but Catalan does not always work the same way.

With places, a is very common and often covers meanings that English expresses with to, at, or sometimes in.

So treballar a l'oficina is the natural Catalan way to say work at the office.

Catalan does use en too, but not in exactly the same way English uses in. In this sentence, a l'oficina is the standard choice.

The word order is quite close to English:

• Si estàs malalta = If you are sick
• no has de treballar = you must not / should not work
• a l'oficina = at the office

Catalan often follows a straightforward order in sentences like this:

if-clause + main clause

The comma after the si clause is also normal in writing, just like in English.

You may see deure used for obligation too:

• deus treballar = you must / should work

But haver de is extremely common and very natural in everyday Catalan for obligation or necessity.

So:

• no has de treballar is a very good, standard choice
• no deus treballar is also possible in some contexts, but it can sound a bit different in force or style depending on region and situation

For a learner, haver de + infinitive is one of the safest and most useful patterns to learn first.

Only some parts would change.

To a man:

• Si estàs malalt, no has de treballar a l'oficina.

To a woman:

• Si estàs malalta, no has de treballar a l'oficina.

To more than one person:

• Si esteu malalts, no heu de treballar a l'oficina.
• Si esteu malaltes, no heu de treballar a l'oficina.

Changes to notice:

• estàs → esteu for you all
• has → heu for you all
• adjective agrees in number and gender:
  • malalt / malalta / malalts / malaltes

Yes. For temporary physical or emotional states, estar is very common.

Examples:

• Estic cansat/cansada = I am tired
• Està malalt/malalta = He/She is sick
• Estem bé = We are well
• Estan contents/contentes = They are happy

So estàs malalta fits a very common pattern in Catalan: estar + adjective for a temporary condition.