Hon har bott hos sin syster i två veckor, men på lördag flyttar hon in.

Har bott is the present perfect of bo (to live / stay).

In this sentence, Hon har bott hos sin syster i två veckor means she started living/staying there two weeks ago and that situation is still true up to now.

A native English speaker may wonder why Swedish does not simply use the present tense. In Swedish, when you talk about something that started in the past and has continued until now, the present perfect is very common:

• Hon har bott där i två veckor. = She has lived / been staying there for two weeks.
• Jag har jobbat här sedan maj. = I have worked / been working here since May.

So har bott fits the idea of an action or state that began earlier and is relevant now.

It can feel like either, depending on context.

The verb bo usually means to live somewhere, but in some situations it can also sound like to stay somewhere, especially when it is temporary.

So:

• Hon har bott hos sin syster i två veckor could be understood as
  She has been living with her sister for two weeks
• In natural English, it might also be translated as
  She has been staying with her sister for two weeks

Because the second part says men på lördag flyttar hon in, it sounds like her current arrangement at her sister’s place is temporary.

Hos means something like at, with, or in the home/business of, depending on context.

Here, hos sin syster means she is staying/living with her sister, usually in the sister’s home.

Examples:

• Jag bor hos mina föräldrar. = I live with my parents.
• Hon är hos läkaren. = She is at the doctor’s.
• Vi ska äta hos Anna. = We are going to eat at Anna’s place.

So hos is often used when talking about being at a person’s place or in their care.

This is a very common question.

Sin/sitt/sina is a reflexive possessive. It is used when the possessor is the subject of the same clause.

In Hon har bott hos sin syster, the subject is hon (she), and the sister belongs to that same she, so Swedish uses sin:

• Hon bor hos sin syster. = She lives with her own sister.

If you said hennes syster, it would normally mean someone else’s sister, not the subject’s:

• Hon bor hos hennes syster. = She lives with her sister
  meaning: some other female person’s sister

So:

• sin syster = her own sister
• hennes syster = another woman’s sister

Because syster is a common gender singular noun.

The reflexive possessive forms are:

• sin for common gender singular nouns
• sitt for neuter singular nouns
• sina for plural nouns

Examples:

• sin syster = her own sister
• sitt hus = her own house
• sina böcker = her own books

Since syster is singular and common gender, sin is correct.

Here it means for two weeks.

This is something that often confuses English speakers, because Swedish i can sometimes look like English in.

In time expressions, i två veckor often means for two weeks, especially with a verb form like har bott, where the action has lasted for that amount of time.

So:

• Hon har bott hos sin syster i två veckor. = She has lived/stayed with her sister for two weeks.

If Swedish wants to say something more like in two weeks in the future sense, context usually makes that clear, and often a different phrasing is used.

Swedish uses på with days of the week when meaning on that day:

• på måndag = on Monday
• på fredag = on Friday
• på lördag = on Saturday

So på lördag simply means on Saturday.

English speakers sometimes expect i, but with days, på is the normal choice.

Swedish usually does not use an article before days of the week in this kind of expression.

So:

• på lördag = on Saturday
• på söndag = on Sunday

That is normal Swedish. You do not need a word corresponding to the here.

Depending on context, på lördag often means this coming Saturday.

Flytta in is a verb + particle combination, and it means move in.

• flytta = move
• in = in

Together:

• flytta in = move into a home/apartment/room

Examples:

• Vi flyttar in nästa vecka. = We’re moving in next week.
• När flyttar du in? = When are you moving in?

In your sentence, men på lördag flyttar hon in means that on Saturday she will move into the new place.

Because Swedish often separates the particle from the verb in a main clause.

So:

• Hon flyttar in på lördag.
• På lördag flyttar hon in.

Both are normal patterns.

This is similar to English phrasal verbs like move in, pick up, turn on, where the parts can feel connected in meaning.

In infinitive form, they stay together more clearly:

• att flytta in = to move in

But in a normal sentence, Swedish often places the particle later:

• Hon flyttar in.

Because Swedish follows the V2 rule in main clauses: the finite verb must come in the second position.

Here, på lördag has been placed first for emphasis or structure. Once that happens, the verb must come next:

• På lördag flyttar hon in.

Not:

• På lördag hon flyttar in.

You can compare:

• Hon flyttar in på lördag.
• På lördag flyttar hon in.

Both are correct, but when på lördag comes first, flyttar must come before hon.

Yes, absolutely.

Both of these are correct:

• Men på lördag flyttar hon in.
• Men hon flyttar in på lördag.

The difference is mainly one of focus and word order.

• Men på lördag flyttar hon in puts more focus on Saturday
• Men hon flyttar in på lördag is a more neutral order

Because Swedish allows different elements to come first, the emphasis can shift a little.

Not necessarily. In fact, it more likely means she has been staying with her sister temporarily, but on Saturday she will move into some other place, probably her own new home.

If she were moving into her sister’s place, the sentence would usually need clearer context.

So the natural interpretation is:

• She has been staying with her sister for two weeks
• On Saturday she finally moves into the place she is going to live in

Swedish often leaves the destination unstated if it is already understood from context.

The comma is used here to separate two main clauses:

• Hon har bott hos sin syster i två veckor
• men på lördag flyttar hon in

This is very natural in written Swedish, especially with men (but), because it helps show the contrast between the two parts.

Even if punctuation styles can vary a little, the comma here is completely normal.

It can match either one, depending on the translation style.

• has lived
• has been living
• sometimes even has been staying

Swedish har bott does not force exactly one English version. English often prefers has been living or has been staying when the situation is temporary or ongoing.

So a natural English rendering could be:

• She has been staying with her sister for two weeks, but on Saturday she moves in.

That does not mean the Swedish grammar is different; it just means English and Swedish do not always line up word for word.