Para la entrevista, quiero un peinado sencillo y natural.

Para expresses purpose or intended use here: for the interview.

So Para la entrevista means for the interview / for the occasion of the interview.

Using por would sound wrong in this sentence, because por usually relates to ideas like cause, movement through, exchange, duration, or means, not intended purpose.

• para la entrevista = for the interview
• not por la entrevista in this meaning

La entrevista usually refers to a specific interview that both speaker and listener can identify, or that is understood from context.

So the sentence suggests something like:

• For the interview I have coming up, I want...

If you said para una entrevista, it would mean for an interview, more general or indefinite.

Both are possible, but they mean slightly different things:

• Para la entrevista... = for the interview
• Para una entrevista... = for an interview

Peinado means hairstyle or hair styling.

It refers to the way the hair is arranged, not the hair itself.

Compare:

• peinado = hairstyle
• pelo / cabello = hair
• corte de pelo = haircut
• peinar(se) = to comb/style one’s hair

So quiero un peinado sencillo y natural means the speaker wants a certain style, not necessarily a haircut.

Un peinado means a hairstyle. The speaker is asking for one possible type of hairstyle, not referring to one already identified.

If you said el peinado, it would sound like a specific hairstyle already known in the conversation.

So:

• quiero un peinado... = I want a hairstyle...
• quiero el peinado... = I want the hairstyle...

In this context, un is the natural choice.

In Spanish, adjectives often come after the noun, especially when they describe a factual quality.

So:

• un peinado sencillo y natural

is the normal order.

English usually says:

• a simple, natural hairstyle

Spanish usually says:

• a hairstyle simple and natural

Putting the adjectives before the noun is sometimes possible in Spanish, but it often changes the tone or sounds less neutral. Here, peinado sencillo y natural is the most natural order.

Yes, here sencillo means simple, not elaborate, or uncomplicated.

For a hairstyle, sencillo suggests:

• neat
• understated
• not too flashy
• appropriate for a professional situation

It does not mean easy in the sense of difficulty. It describes the style.

In this sentence, sencillo y natural is a very common combination for talking about appearance.

Quiero means I want, and it is completely possible here. It is direct and natural.

But in real-life situations, especially when speaking to a hairdresser, many speakers would soften it a bit:

• Quiero un peinado sencillo y natural.
• Me gustaría un peinado sencillo y natural.
• Quisiera un peinado sencillo y natural.

These all work, but the tone changes:

• quiero = direct
• me gustaría = more polite / softer
• quisiera = polite, slightly more formal

So the original sentence is correct, but not the only natural option.

Yes. In Spanish, adjectives usually agree in gender and number with the noun they describe.

Since peinado is masculine singular, the adjectives must match:

• sencillo
• natural

Notice:

• sencillo changes:
  
  • masculine singular: sencillo
  • feminine singular: sencilla
  • masculine plural: sencillos
  • feminine plural: sencillas
• natural changes only in number:
  • singular: natural
  • plural: naturales

So:

• un peinado sencillo y natural
• una apariencia sencilla y natural
• peinados sencillos y naturales

Yes. Both are correct, but they are used in slightly different situations.

• Para la entrevista = for the interview, a specific one
• Para una entrevista = for an interview, more generally

For example:

• Para la entrevista, quiero un peinado sencillo y natural.
  You mean a particular interview.
• Para una entrevista, conviene llevar un peinado sencillo y natural.
  This means interviews in general.

So the choice depends on whether the interview is specific or generic.

The comma separates the opening context phrase Para la entrevista from the main clause quiero un peinado sencillo y natural.

It is similar to English when you begin with a short introductory phrase:

• For the interview, I want...

In Spanish, this comma is natural and helps readability, though in very short sentences punctuation can sometimes vary. Here, the comma is perfectly normal.

Yes, it sounds natural and correct in Spain.

It is clear, standard Spanish, and appropriate in a context like speaking about how you want to look for a job interview.

That said, in a real salon conversation in Spain, someone might also say:

• Para la entrevista, me gustaría un peinado sencillo y natural.
• Quiero algo sencillo y natural para la entrevista.

These may sound a little more conversational, but the original sentence is absolutely natural.