Li vaig dir que aquella joguina gairebé sempre era a la meva bossa quan jo era petita.

Li is an indirect object pronoun. Here it means to him, to her, or to you (formal singular).

So:

Li vaig dir = I told him/her/you

Catalan often uses these short pronouns before the verb. By itself, li does not tell you whether the person is male or female; the context does that.

No. In modern Catalan, vaig + infinitive is a very common past tense called the periphrastic past.

So:

• dic = I say
• vaig dir = I said / I told
• he dit = I have said

Even though vaig originally comes from anar (to go), in this structure it does not mean movement. Vaig dir just means I said / I told.

Que introduces the next clause, like English that.

So:

• Li vaig dir que... = I told him/her that...

In English, that is often omitted: I told her the toy was...
In Catalan, que is usually kept.

Because aquella means that, while aquesta means this.

Catalan makes a distinction like this:

• aquesta joguina = this toy
• aquella joguina = that toy

Also, aquella has to agree with joguina, which is feminine singular, so you get:

• aquell for masculine singular
• aquella for feminine singular

Gairebé means almost, and sempre means always.

Together:

gairebé sempre = almost always

It is placed before era because it modifies the idea of was:

aquella joguina gairebé sempre era a la meva bossa
= that toy was almost always in my bag

Era is the imperfect of ser, and the imperfect is used for:

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

Here, gairebé sempre strongly suggests a habit or repeated pattern, so era is the natural choice:

• era a la meva bossa = it was / used to be in my bag

If you said va ser, it would sound more like one completed occasion.

This is a very common question for English speakers, especially if they also know Spanish.

In Catalan, ser is often used for simple location, especially in neutral statements about where something is:

• On és la joguina? És a la bossa.
  = Where is the toy? It is in the bag.

So era a la meva bossa is perfectly normal.

Estar can also appear in some contexts or varieties, often with a slightly stronger sense of temporary state or placement, but ser is very natural here.

Catalan often uses a where English would use in or at.

So:

• era a la meva bossa = it was in my bag

If you want to stress the idea of being physically inside, Catalan can also say:

• dins de la meva bossa
• dintre de la meva bossa

But a la meva bossa is a normal everyday way to say it.

Because Catalan normally uses the definite article with possessives.

So:

• la meva bossa = my bag
• el meu llibre = my book
• les meves claus = my keys

This is different from English, where you normally just say my bag without the.

Jo is optional here. Catalan often leaves subject pronouns out because the verb already shows the person:

• quan era petita = when I was little
• quan jo era petita = same meaning, but with extra emphasis or clarity

Petita is feminine singular, so it tells you the speaker is female. A male speaker would say:

• quan jo era petit

So this part means when I was little, with the adjective agreeing with the speaker.