Läkaren säger att hon måste andas långsamt och vila.

Because läkaren is the definite form of läkare.

• en läkare = a doctor
• läkaren = the doctor

In Swedish, the definite article is often attached to the end of the noun instead of being a separate word like the in English.

It can mean either, depending on context.

Swedish present tense often covers both:

• Läkaren säger ... = The doctor says ...
• It can also be understood as The doctor is saying ... if the situation makes that clear.

So Swedish does not always make the same simple present / present continuous distinction that English does.

Here att means that.

So:

• Läkaren säger att ... = The doctor says that ...

In English, that is often optional, but in Swedish att is very common in this kind of sentence. You may sometimes hear it omitted in informal speech, but keeping att is completely natural and standard.

Not necessarily.

Hon just means she, so it refers to some female person already known from the context. Without more context, it could mean:

• the doctor herself, if the doctor is female
• another woman or girl being talked about

So the sentence is grammatically clear, but the exact referent of hon depends on the wider context.

Because after a modal verb like måste, Swedish normally uses the next verb in the infinitive without att.

Examples:

• hon måste andas = she must breathe
• hon måste vila = she must rest
• jag kan komma = I can come
• vi vill äta = we want to eat

So this works much like English must breathe, not must to breathe.

No, not here. Andas is a deponent verb: a verb that looks like an -s passive form but actually has an active meaning.

So:

• andas = to breathe

It does not mean to be breathed in this sentence. This is just the normal dictionary form of the verb.

A useful extra point: for some deponent verbs, the infinitive and the present tense look the same, and andas is one of them.

Because långsamt is the adverb form here, meaning slowly.

It comes from the adjective långsam = slow.

• en långsam person = a slow person
• andas långsamt = breathe slowly

In many cases, Swedish forms an adverb from an adjective by using the -t form.

Because both verbs are connected to the same måste.

• hon måste andas långsamt och vila

This means:

• she must breathe slowly
• and she must rest

Swedish, like English, usually avoids repeating the modal when it is shared:

• She must breathe slowly and rest
• not usually She must breathe slowly and must rest

After att, you have a subordinate clause, and the normal order here is:

• att + subject + finite verb + rest

So:

• att hon måste andas långsamt och vila

This is very normal Swedish word order.

A useful thing to know: in subordinate clauses, words like inte usually come before the finite verb:

• att hon inte måste vila

That is different from main clause word order, where Swedish often puts the finite verb earlier.

A rough English-friendly guide:

• Läkaren ≈ LEH-ka-ren
• säger ≈ SEH-yer
• måste ≈ MOS-teh or MAW-steh depending on accent
• långsamt ≈ LONG-samt
• vila ≈ VEE-la

A couple of vowel tips:

• ä is somewhat like the e in bed, but often longer
• å is roughly like the vowel in law

These are only approximations, but they can help you get started.