Jo seia al seu costat amb un coixí i escoltava un conte.

Yes. In Catalan, the verb ending often already shows the subject, so seia by itself can mean I was sitting.

That means jo is optional here. It may be used for:

• emphasis
• contrast with someone else
• clarity, if the context could be ambiguous

So both are possible:

• Jo seia al seu costat...
• Seia al seu costat...

The second one is often the more neutral choice.

Both are in the imperfect tense.

The imperfect is commonly used for:

• ongoing actions in the past
• background description
• repeated or habitual past actions

So here, the sentence is presenting a scene in progress: the speaker was sitting and was listening.

Because the sentence describes background action, not a single finished event.

Compare the idea in English:

• I was sitting by their side and listening to a story → ongoing scene
• I sat down by their side and listened to a story → more like completed actions

In Catalan, the imperfect works very naturally for that first kind of meaning. It helps create the feeling of a moment unfolding.

They are both imperfect, but they come from different verbs and different conjugation patterns:

• seia ← seure (to sit)
• escoltava ← escoltar (to listen)

Catalan verbs do not all form the imperfect in the same way:

• many -ar verbs use endings like -ava → escoltava
• verbs like seure form it differently → seia

So the tense is the same, but the verb class is different.

Seia is the imperfect of seure, meaning to sit.

It is close in meaning to estar assegut / estar asseguda (to be seated / to be sitting), but there is a small difference in feel:

• seia = was sitting, focusing on the action/posture
• estava assegut/asseguda = was seated, focusing more on the state

In many contexts, both could be translated as was sitting, but they are not always identical in tone.

Because al is the contraction of a + el.

Here:

• a = at / to
• el costat = the side

So:

• a + el costat → al costat

This is very common in Catalan.
Al seu costat means by his/her/your/their side or next to him/her/them.

By itself, seu can mean several things depending on context:

• his
• her
• your (formal singular)
• their

So al seu costat is ambiguous on its own. The context tells you whose side it is.

Also, seu agrees with the thing possessed, not the possessor. Since costat is masculine singular, the form is seu.

For example:

• el seu llibre = his/her/their book
• la seva cadira = his/her/their chair

Yes. Both are possible, but they are used a little differently.

• al seu costat = by his/her side, often smoother and more natural in many contexts
• al costat d’ell / d’ella = next to him / her, more explicit

Catalan often prefers the possessive structure when English might use a pronoun:

• al seu costat
• a la seva dreta
• a la seva vora

So the sentence sounds very natural as written.

Literally it means with a cushion/pillow.

It tells us that the speaker was sitting there with a pillow/cushion, but it does not specify exactly how it was being used. Depending on context, it could mean:

• holding one
• resting on one
• having one nearby

So the phrase is grammatically simple, but semantically a bit open.

Usually, escoltar means to listen, while sentir means to hear or to feel.

So:

• escoltava un conte = was listening to a story
• sentia un conte would sound less natural if you mean active listening

If the idea is that the person was paying attention to the story, escoltava is the right choice.

Not exactly.

Conte usually means:

• a tale
• a short story
• often a story told aloud, especially to a child

Història is broader and can mean:

• story
• history

So escoltava un conte strongly suggests listening to a narrated tale, which fits the sentence very well.

Catalan word order is fairly flexible, though some orders sound more natural than others.

The original sentence is perfectly natural:

• Jo seia al seu costat amb un coixí i escoltava un conte.

You could also rearrange parts for emphasis, for example:

• Al seu costat, jo seia amb un coixí i escoltava un conte.

But the original order is clear and neutral. In everyday Catalan, that is often the best choice.