Antes de empezar a cocinar, me pongo el delantal y abro la ventana de la cocina.

Because antes needs de before a noun or an infinitive.

So Spanish uses:

• antes de + noun
• antes de + infinitive

Examples:

• antes de la cena = before dinner
• antes de salir = before leaving
• antes de empezar = before starting

Without de, it would be incorrect here.

Because empezar is commonly followed by a + infinitive when you say you begin doing something.

So:

• empezar a cocinar = to start cooking
• empezar a leer = to start reading
• empezar a trabajar = to start working

This is just the normal pattern of the verb empezar in this meaning.

Yes, you could, and it would sound natural.

The difference is small:

• antes de cocinar = before cooking
• antes de empezar a cocinar = before starting to cook

The version in the sentence is a bit more explicit and emphasizes the moment right before the cooking begins.

Because ponerse means to put on something on yourself, especially clothes or accessories.

• poner = to put, to place
• ponerse = to put on oneself

So:

• pongo el libro en la mesa = I put the book on the table
• me pongo el delantal = I put on the apron

The me shows that the action is being done to yourself.

This is very common in Spanish with clothing, body parts, and personal items when the owner is obvious.

Spanish often prefers:

• me pongo el abrigo
• me lavo las manos
• me quito los zapatos

Even though English usually says my, Spanish often uses the because the reflexive pronoun already shows whose item it is.

So me pongo el delantal naturally means I put on my apron in context.

Yes.

The difference is:

• me pongo el delantal = I put on the apron / the apron I normally use / the known apron
• me pongo un delantal = I put on an apron

So el sounds specific, while un sounds non-specific.

Because Spanish often leaves out subject pronouns when the verb ending already makes the subject clear.

Here:

• me pongo
• abro

Both forms clearly show I.

So yo is not necessary. You could say yo me pongo... y abro..., but it would usually be for emphasis, contrast, or clarity.

Spanish often uses the present tense to describe routines, habits, or a sequence of actions that usually happen.

So this sentence sounds like someone describing their normal routine:

• Antes de empezar a cocinar, me pongo el delantal y abro la ventana de la cocina.

It means something like Before I start cooking, I put on my apron and open the kitchen window as a regular action.

They are different:

• ponerse = to put on
• llevar = to wear

Examples:

• Me pongo el delantal. = I put on the apron.
• Llevo un delantal. = I am wearing an apron.

So ponerse focuses on the action of dressing, while llevar describes the state afterward.

This means the kitchen window literally as the window of the kitchen.

Spanish often uses de to show this kind of relationship:

• la puerta de la casa = the house door / the door of the house
• la mesa del comedor = the dining-room table
• la ventana de la cocina = the kitchen window

It specifies which window is being opened.

Because la cocina is a specific noun phrase: the kitchen.

In Spanish, when you say window of the kitchen, you normally keep the article:

• la ventana de la cocina

Saying de cocina would not sound natural in this sentence.

It is natural and correct here.

That first part is an introductory phrase, and Spanish often separates a longer introductory phrase with a comma:

• Antes de empezar a cocinar, ...

In very short phrases, commas are sometimes omitted, but in this sentence the comma helps readability and sounds standard.

Yes. In Spain, delantal is the normal everyday word for apron.

In some Latin American countries, you may also hear mandil, but delantal is the standard choice for Spain.