Voy a cambiar la silla de sitio para sentarme junto a la ventana.

Voy a cambiar is the near future in Spanish, literally I am going to move/change. It is extremely common in everyday speech.

So:

• Voy a cambiar la silla... = I’m going to move the chair...
• A more formal or less immediate alternative would be Cambiaré la silla... = I will move the chair...

In normal conversation, Spanish often prefers ir a + infinitive, just like English often prefers I’m going to... over I will....

Here cambiar ... de sitio is an expression meaning to move something to a different place/position.

So cambiar la silla de sitio does not mean changing the chair into something else. It means:

• to move the chair
• more literally: to change the chair’s place

You will also hear:

• mover la silla = to move the chair
• cambiar la silla de lugar = similar idea

In this sentence, de sitio is the key part that shows it is about location.

Yes. Mover la silla is very natural and probably the most direct option.

Compare:

• Voy a mover la silla... = I’m going to move the chair...
• Voy a cambiar la silla de sitio... = I’m going to move the chair to a different spot...

The second version slightly emphasizes changing its place. Both are correct and natural.

In Spanish, articles are used more often than in English. Here la silla means the chair, referring to a specific chair.

So:

• Voy a cambiar la silla de sitio = I’m going to move the chair
• Voy a cambiar una silla de sitio = I’m going to move a chair

If the speaker has a particular chair in mind, la silla is the natural choice.

Sitio means place, spot, or location. In the expression de sitio, it helps express the idea of from one place to another or to a different spot.

Useful related expressions:

• cambiar de sitio = to move places / change position
• muévete de sitio = move somewhere else
• este no es mi sitio = this is not my place/spot

So in your sentence, de sitio is not being translated word-for-word into English, but it is essential in Spanish.

Because sentarse is the verb to sit down, and it is reflexive.

• sentar usually means to seat someone or can have other meanings
• sentarse means to sit down oneself

So:

• para sentarme = in order to sit down
• literally: for myself to sit down

The -me is the reflexive pronoun meaning myself.

Examples:

• Voy a sentarme. = I’m going to sit down.
• Voy a sentar al niño. = I’m going to seat the child.

That is an important difference.

In Spanish, when you have an infinitive, a reflexive pronoun can be attached to the end.

So these are equivalent in structure:

• para sentarme
• para me sentar ❌ not correct

With an infinitive, the pronoun must attach:

• sentarme
• sentarte
• sentarse
• sentarnos
• sentaros
• sentarse

In your sentence:

• para = in order to
• sentarme = sit down myself / sit down

Together: para sentarme = in order to sit down

Para introduces purpose. It answers the question what for?

• Voy a cambiar la silla de sitio para sentarme junto a la ventana.
• I’m going to move the chair so that I can sit by the window.

So para + infinitive is a very common pattern when the subject stays the same.

More examples:

• Estudio para aprender. = I study in order to learn.
• Abro la ventana para respirar mejor. = I open the window to breathe better.

Because the same person is doing both actions, Spanish uses para + infinitive.

Both mean next to / by the window.

• junto a la ventana = next to / beside the window
• al lado de la ventana = next to / at the side of the window

Junto a can sound a little more compact or slightly more written/formal, but it is very normal.
Al lado de is also extremely common and very natural in speech.

So you could also say:

• Voy a mover la silla para sentarme al lado de la ventana.

Same basic meaning.

Because the expression is junto a = next to / beside.

It works as a fixed combination:

• junto a la puerta = next to the door
• junto al coche = next to the car
• junto a la ventana = next to the window

It is similar to learning a preposition as a chunk. It is best to remember junto a together.

Yes. In many contexts, it can simply mean by the window or near the window, depending on the situation.

Literally, junto a suggests closeness, often right beside, but in natural English translation by the window is often the most idiomatic choice.

So the exact force depends on context:

• very literal: next to the window
• natural English: by the window

This is a very normal Spanish word order:

• para
  • infinitive phrase
• then the location phrase

So:

• para sentarme junto a la ventana = in order to sit by the window

You could sometimes rearrange parts for emphasis, but the original order is the most neutral and natural.

For example:

• Voy a cambiar la silla de sitio para sentarme junto a la ventana. ✅ natural
• Para sentarme junto a la ventana, voy a cambiar la silla de sitio. ✅ also correct, but the purpose is emphasized first

Strictly speaking, sentarse usually means to sit down, focusing on the action of taking a seat.

So:

• para sentarme = to sit down

But in smooth English, people often say:

• to sit by the window

because sit down by the window can sound slightly heavier in some contexts.

So the best translation depends on whether you want:

• literal precision: to sit down by the window
• natural English: to sit by the window

Both can work.

No. That is incorrect.

With an infinitive, the reflexive pronoun must stay attached:

• sentarme ✅
• sentar me ❌

The same pattern applies to many verbs:

• quiero acostarme = I want to go to bed
• voy a lavarme = I’m going to wash myself
• necesito vestirme = I need to get dressed

So in your sentence, sentarme must stay as one unit.

Yes, it sounds perfectly natural in Spain. Nothing in it is exclusively Spain-only, but a few features fit very well with standard Peninsular Spanish:

• voy a + infinitive is very common
• cambiar ... de sitio is very natural
• junto a is a normal choice in Spain
• sentarme is standard everywhere

In other Spanish-speaking regions, the sentence would still be understood and would usually sound natural too, though some speakers might more quickly choose mover la silla or al lado de la ventana.