Después de ponerme el pijama, me gusta leer un rato en el sofá.

In Spanish, when you use an infinitive like poner, an attached object or reflexive pronoun usually goes onto the end of the infinitive:

• ponerme
• lavarme
• vestirme

After después de, Spanish normally uses an infinitive if the subject stays the same:

• Después de cenar...
• Después de ducharme...
• Después de ponerme el pijama...

So después de ponerme is the natural structure.
Después de me poner is not correct Spanish.

Literally, it means to put the pyjamas on myself.

Breakdown:

• poner = to put
• me = on myself / to myself
• el pijama = the pyjamas / pajamas

In natural English, we would usually say to put on my pyjamas.

Spanish often uses a reflexive pronoun in clothing expressions:

• me pongo la chaqueta = I put on my jacket
• se quitó los zapatos = he/she took off his/her shoes

This is very common in Spanish. With clothes, body parts, and personal items, Spanish often uses the definite article (el, la, los, las) instead of a possessive like mi or tu, especially when it is already clear whose thing it is.

So:

• ponerme el pijama = put on my pyjamas
• me duele la cabeza = my head hurts
• se lavó las manos = he/she washed his/her hands

Because me already tells us the pyjamas are connected to me, el pijama sounds natural.

Because gustar works differently from English to like.

Spanish expresses the idea more like:

• me gusta leer = reading is pleasing to me

So:

• me = to me
• gusta = is pleasing
• leer un rato en el sofá = reading for a while on the sofa

That is why you do not say yo gusto leer for I like reading.

The verb agrees with what is liked, not with the person who likes it.

Here, what is pleasing is the whole action:

• leer un rato en el sofá

A whole infinitive phrase counts as singular, so Spanish uses gusta.

Compare:

• Me gusta leer. = I like reading.
• Me gustan los libros. = I like books.

In the second example, los libros is plural, so you get gustan.

Un rato means for a while or a little while.

So:

• leer un rato = to read for a while

It is a very common, natural expression in Spanish:

• Voy a descansar un rato. = I’m going to rest for a while.
• Hablamos un rato. = We talked for a while.

It does not usually mean a precise amount of time.

Spanish often expresses duration without a direct equivalent of English for.

So English:

• read for a while

becomes Spanish:

• leer un rato

This is completely normal. Spanish can express time duration directly:

• Dormí dos horas. = I slept for two hours.
• Espera un momento. = Wait for a moment.

En el sofá means on the sofa or on the couch.

It tells you where the reading happens.

Yes, you could also say en el sillón, but the meaning changes slightly:

• sofá = sofa / couch
• sillón = armchair

So the original sentence specifically means reading on the sofa, not in an armchair.

The sentence begins with a time expression:

• Después de ponerme el pijama = after putting on my pyjamas

This sets the scene first, and then comes the main idea:

• me gusta leer un rato en el sofá

This is a very natural word order in Spanish. You could also say:

• Me gusta leer un rato en el sofá después de ponerme el pijama.

That is also grammatical, but the original version highlights the after... part more clearly.

Yes, ponerme el pijama is much more natural.

Spanish usually says:

• ponerse el pijama
• ponerse la chaqueta
• ponerse los zapatos

Vestirse con el pijama is understandable, but it sounds less idiomatic for this everyday action. It can feel more like to dress oneself in pyjamas, which is not the most common everyday phrasing.

Yes. In Spanish, pijama is normally singular:

• el pijama

Even though English often uses the plural pyjamas, Spanish treats it as one item of clothing.

So:

• Me pongo el pijama. = I put on my pyjamas.

This is one of those vocabulary differences where Spanish and English divide things differently.

In standard Spanish, especially in Spain, el pijama is the usual form.

Some learners may hear plural-looking English influence and want to say los pijamas, but that is generally not the standard choice for this meaning. El pijama is the safer and more natural option.

The comma separates the introductory time phrase from the main clause:

• Después de ponerme el pijama, = introductory element
• me gusta leer un rato en el sofá. = main clause

In Spanish, this comma is very natural and helps readability. Even if punctuation can vary a little in some contexts, here the comma is a good standard choice.

Yes. Both are good translations.

• Me gusta leer = I like to read
• Me gusta leer = I like reading

In Spanish, the infinitive leer covers both ideas naturally. English has two common ways to express it, but Spanish just uses the infinitive here.