Pongo la ropa sucia en la lavadora antes de cenar.

Poner is the infinitive form (to put).
In Spanish, when you have a subject (here: I), you normally conjugate the verb, just like English chooses between put, puts, putting, etc.

• Poner = to put (infinitive, dictionary form)
• Pongo = I put (1st person singular, present tense)

So:

• Pongo la ropa sucia en la lavadora… = I put the dirty clothes in the washing machine…
• Poner la ropa sucia en la lavadora… would be more like to put the dirty clothes in the washing machine… (used after another verb, e.g. Tengo que poner la ropa sucia en la lavadora – I have to put…).

Here we’re making a full sentence with I as subject, so pongo is required.

In Spanish, subject pronouns (yo, tú, él, etc.) are usually optional because the verb ending already tells you who the subject is.

• Pongo la ropa sucia en la lavadora.
• Yo pongo la ropa sucia en la lavadora.

Both are grammatically correct and mean I put the dirty clothes in the washing machine.
But:

• Pongo… (without yo) is the most natural in everyday speech.
• Yo pongo… is used for emphasis or to contrast with someone else:
  
  • Yo pongo la ropa y tú la tiendes. – I put the clothes in and you hang them up.

In Spanish, ropa is normally a mass noun (uncountable), like furniture or luggage in English.

• la ropa = clothes (in general), not a piece of clothing
• la ropa sucia = dirty clothes / laundry

You very rarely use ropas in modern everyday Spanish; that sounds old-fashioned or very literary.

So even though English says clothes (plural), Spanish treats ropa as a singular noun and uses a singular article and adjective:

• la ropa limpia – clean clothes
• la ropa sucia – dirty clothes

Adjectives in Spanish agree with the grammatical gender and number of the noun, not with the real-world quantity.

• Noun: la ropa – feminine, singular
• Adjective: must also be feminine, singular → sucia

So:

• la ropa sucia – the dirty clothes
• If you had a clearly plural noun, e.g. las camisetas, then you’d say:
  
  • las camisetas sucias – the dirty t‑shirts

It feels plural in meaning, but grammar follows the form of ropa (singular), so sucia is correct.

Both are possible, but there is a nuance:

• Pongo la ropa sucia en la lavadora.
  
  • Sounds like specific dirty clothes that are understood from context (e.g. the laundry in the basket today).
• Pongo ropa sucia en la lavadora.
  
  • Sounds more like some dirty clothes, non-specific; you’re just describing what you are putting in, not “the” known set.

In everyday speech about your usual laundry, la ropa sucia is more natural, because you and your listener know what laundry you mean.

Yes, and it’s quite common:

• Pongo la ropa sucia en la lavadora.
  
  • Very common; neutral: I put the dirty clothes in the washing machine.
• Meto la ropa sucia en la lavadora.
  
  • Also very natural; literally I put/insert the dirty clothes into the washing machine.

Nuance:

• poner focuses slightly more on placing something somewhere.
• meter focuses more on putting something inside a container or enclosed space.

For a washing machine, poner and meter are both used in Spain and are both fine.

There is also the everyday expression in Spain:

• Pongo la lavadora. – I put the washing machine on / I do a load of washing.
  (Here la lavadora is the direct object: I run the washing machine.)

En is the standard preposition for in / on / at when talking about location:

• en la lavadora = in the washing machine

Alternatives:

• dentro de la lavadora – literally inside the washing machine.
  
  • More explicit about the interior, used if you want to stress inside, but in most contexts en la lavadora is enough.
• a la lavadora would generally be wrong here.
  
  • a is more about direction (to):
    
    • Voy a la lavadora. – I’m going to the washing machine.
  • Not used for the location of the clothes in this sentence.

So for where you put the clothes, en la lavadora is the natural, default choice.

In Spain:

• lavadora = the washing machine for clothes.
• The machine for dishes is el lavavajillas (also lavaplatos in some places, but lavavajillas is very common in Spain).

So Pongo la ropa sucia en la lavadora can only be understood as the clothes-washing machine, not a dishwasher.

In Spanish, when a verb comes after a preposition (like de, a, por, sin), it must be in the infinitive form, and the preposition cannot be dropped.

• antes de + infinitive is the correct structure:
  
  • antes de cenar – before having dinner
  • antes de salir – before going out
  • antes de estudiar – before studying

So:

• ❌ antes cenar – incorrect
• ✅ antes de cenar – correct

Both are correct, but they focus on slightly different things:

• antes de cenar – before having dinner (focus on the action).
  
  • Very common and natural for routines:
    
    • Siempre me ducho antes de cenar. – I always shower before having dinner.
• antes de la cena – before dinner (the event/meal) (focus on the event / moment).
  
  • More like a point on a schedule or occasion:
    
    • Hablaremos antes de la cena. – We’ll talk before dinner (as an event).

In the original sentence about a routine household action, antes de cenar sounds more natural.

No. That form is not correct.

With antes de que, Spanish normally requires the subjunctive, and you must keep que:

• antes de que + subjunctive

Examples:

• Pongo la ropa en la lavadora antes de que cenemos.
  – I put the clothes in the washing machine before we have dinner.
  (subject changes from I to we, so clause with que.)

Compare:

• antes de cenar – before having dinner (same subject as the main verb: I put, I have dinner).
• antes de que cenemos – before we have dinner (introduces a different subject, we).

So:

• ❌ antes de que ceno (wrong tense & mood)
• ✅ antes de cenar (same subject, infinitive)
• ✅ antes de que cene / cenemos, etc. (different subject, subjunctive)

Yes, but the meaning changes slightly.

• Pongo la ropa sucia en la lavadora antes de cenar.
  
  • Present simple: describes a habit / routine.
  • Implies you generally do this before dinner.
• Estoy poniendo la ropa sucia en la lavadora (ahora).
  
  • Present continuous: describes something happening right now.
  • You’d say this if someone asked What are you doing?

To keep the habitual meaning I (normally) put the dirty clothes in the washing machine before dinner, you want the present simple: pongo.

Yes, that is exactly how you would do it.

• La ropa sucia is feminine singular → direct object pronoun: la.
• Pronoun position with a simple conjugated verb: before the verb.

So:

• Pongo la ropa sucia en la lavadora antes de cenar.
• La pongo en la lavadora antes de cenar. – I put it in the washing machine before dinner.

If you had a compound form like voy a poner, you could put the pronoun:

• Before the conjugated verb:
  
  • La voy a poner en la lavadora.
• Or attached to the infinitive:
  
  • Voy a ponerla en la lavadora.

Both are correct and common.

Yes. In Spain you will often hear:

• Hacer la colada. – to do the laundry
  
  • Suelo hacer la colada antes de cenar. – I usually do the laundry before dinner.

And also:

• Poner la lavadora. – to put a load in / run the washing machine
  
  • Pongo la lavadora antes de cenar.

Your sentence focuses on the physical action of putting the dirty clothes in (Pongo la ropa sucia en la lavadora), while hacer la colada and poner la lavadora talk about the whole task of doing a wash.