Debo planchar la camisa antes de la entrevista.

Because Spanish often leaves out subject pronouns when they are clear from the verb form. Debo already means I must / I should / I have to.

You can say yo debo, but it usually adds emphasis or contrast, for example:

• Yo debo planchar la camisa, no tú. — I have to iron the shirt, not you.

In a normal sentence, debo by itself is the most natural choice.

Debo is the first person singular present tense of deber.

Here, deber + infinitive expresses obligation or necessity, so debo planchar means something like:

• I must iron
• I should iron
• I have to iron

The exact English translation depends on context, but the structure is very common in Spanish.

Because after deber, the next verb stays in the infinitive.

So the pattern is:

• deber + infinitive

Examples:

• Debo estudiar. — I must study.
• Debes salir. — You must leave.
• Debemos comer. — We must eat.

So in your sentence:

• Debo planchar la camisa = I must iron the shirt

Both can express obligation, and in many situations both are possible:

• Debo planchar la camisa
• Tengo que planchar la camisa

A learner-friendly way to think about it is:

• debo = I should / I must
• tengo que = I have to

But in real life, the difference is often small. Sometimes debo can sound a little more formal, reflective, or less forceful than tengo que, depending on context and speaker.

Spanish often uses the definite article (el, la, los, las) where English would use a possessive like my or your, especially when the owner is obvious from context.

So la camisa can naturally mean the shirt or my shirt, depending on the situation.

In this sentence, if it is clear that the speaker means their own shirt, la camisa sounds very natural.

You could also say mi camisa if you want to be more explicit:

• Debo planchar mi camisa antes de la entrevista.

Both are correct, but la camisa is very common Spanish usage.

Antes de means before.

It is followed by:

• a noun:
  antes de la entrevista — before the interview
• an infinitive:
  antes de salir — before leaving / before I leave

So the de is required here. You do not say just antes la entrevista.

This is a fixed pattern:

• antes de + noun
• antes de + infinitive

Because entrevista is a feminine noun, so it takes la:

• la entrevista

The contraction del only happens with de + el:

• de + el = del

But there is no contraction with de + la:

• de la stays de la

So:

• antes de la entrevista ✅
• antes del entrevista ❌

The noun is la entrevista, so it is feminine.

Like many nouns ending in -a, it is feminine, although noun gender always has to be learned with the word itself.

That affects the article and any adjectives:

• la entrevista
• una entrevista
• la entrevista importante

So in this sentence, la matches entrevista because it is feminine singular.

In this sentence, yes, the definite article sounds natural because it refers to a specific interview that both speaker and listener can identify.

• antes de la entrevista = before the interview

If you were speaking more generally or introducing it for the first time, you might say:

• antes de una entrevista = before an interview

But antes de entrevista by itself would usually sound incomplete or unnatural in standard Spanish.

In standard Spanish, deber + infinitive and deber de + infinitive are usually treated differently:

• deber + infinitive = obligation
  Debo planchar la camisa. — I must / should iron the shirt.

• deber de + infinitive = probability or assumption
  Debo de estar cansado. — I must be tired / I’m probably tired.

So in your sentence, debo planchar is the correct standard form because it expresses obligation, not probability.

Yes. The original order is completely natural:

• Debo planchar la camisa antes de la entrevista.

But you can also move the time phrase to the front for emphasis:

• Antes de la entrevista, debo planchar la camisa.

Both are correct. The first is the more neutral, everyday order.

A simple pronunciation guide is:

DEH-bo plan-CHAR la ka-MEE-sa AN-tes de la en-treh-BEES-ta

A few helpful points:

• debo: the b is not like a strong English b all the time; Spanish b and v are pronounced very similarly.
• planchar: ch sounds like English ch in church.
• camisa: stress on mi.
• entrevista: stress on vis.

In most of Spain, this will sound natural with clear vowel sounds and lighter consonants than in English.