Quan la meva mare es troba millor, torna a caminar i ja no li fa mal el braç.

Yes, trobar by itself usually means to find.

But trobar-se is a common pronominal/reflexive form that often means to feel, to be, or to find oneself in a certain state.

So:

• trobar = to find
• trobar-se bé = to feel well
• trobar-se millor = to feel better

In this sentence, la meva mare es troba millor means my mother feels better or my mother is feeling better.

Quan means when.

It introduces a time clause:

• Quan la meva mare es troba millor = When my mother feels better

Catalan often uses the present tense in clauses like this where English may also use the present:

• When my mother feels better, ...

So this is natural Catalan.

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

• Quan la meva mare es troba millor, = When my mother feels better,
• torna a caminar i ja no li fa mal el braç. = she walks again and her arm no longer hurts

This is similar to English, where a comma is also often used after an initial clause.

Literally, torna a caminar is something like returns to walk.

But naturally, it means:

• walks again
• starts walking again
• is able to walk again

Here:

• tornar a + infinitive = to do something again

Examples:

• Torna a provar-ho = Try it again
• Torno a llegir aquest llibre = I’m reading this book again

So torna a caminar means she walks again / she starts walking again.

Because the pattern is:

• tornar a + infinitive

This is a fixed and very common structure meaning to do something again.

So:

• tornar a caminar = to walk again
• tornar a menjar = to eat again
• tornar a dormir = to sleep again

You should learn tornar a as a chunk.

Ja no means no longer, not anymore, or not any more.

In the sentence:

• ja no li fa mal el braç = her arm doesn’t hurt anymore / her arm no longer hurts

Breakdown:

• ja = already / now
• no = not

Together, ja no often expresses that something used to happen but now it does not.

Examples:

• Ja no plou = It’s not raining anymore
• Ja no hi viu = He/She doesn’t live there anymore

Li means to him / to her / to you (formal singular).

Here it refers to la meva mare.

So:

• li fa mal el braç literally = the arm causes pain to her
• natural English = her arm hurts

Catalan often uses an indirect object pronoun with body parts:

• Em fa mal el cap = My head hurts
  literally: The head causes pain to me
• Li fa mal el braç = His/Her arm hurts

So li is there because the pain is happening to her.

Because Catalan usually expresses physical pain with the structure:

• (pronoun) + fa mal + body part

So:

• Em fa mal el peu = My foot hurts
• Et fan mal les mans = Your hands hurt
• Li fa mal el braç = His/Her arm hurts

This is much more natural than using a possessive like el seu braç in this context.

Catalan, like Spanish and some other Romance languages, often uses:

• an indirect object pronoun (em, et, li, ens, us, els)
• plus the definite article (el, la, els, les)

rather than a possessive adjective.

Because with body parts, Catalan normally prefers:

• indirect object pronoun + definite article

So instead of saying her arm, Catalan often says the equivalent of the arm to her:

• li fa mal el braç

This is a very common Romance-language pattern.

Using el seu braç is grammatically possible in some contexts, but here it sounds less natural and less idiomatic.

Fer mal literally means to do harm, but very often it means:

• to hurt
• to cause pain

So:

• Em fa mal = It hurts
• Em fa mal l’esquena = My back hurts
• Li fa mal el braç = His/Her arm hurts

Notice that fa is from fer (to do / to make).

Because the subject is singular:

• el braç = the arm

So:

• el braç fa mal = the arm hurts

If the body part were plural, then you would use fan:

• les cames fan mal = the legs hurt
• li fan mal els ulls = his/her eyes hurt

In this sentence, el braç is singular, so fa is correct.

Both are possible, but li fa mal el braç is a very common and natural order in Catalan.

Catalan often places the indirect object pronoun before the verb:

• li fa mal el braç

This structure foregrounds the experience of pain to her.

You may also hear:

• El braç li fa mal

That can sound more emphatic or more focused on the arm itself.

But the version in your sentence is very standard.

Here millor is best understood as part of the expression trobar-se millor, meaning to feel better.

It functions like better in English.

Compare:

• Està millor = He/She is better
• Em trobo millor = I feel better

So you do not need to worry too much about forcing a strict English-style label here; the important thing is to learn the expression:

• trobar-se millor = to feel better

Catalan often uses the present tense in subordinate clauses introduced by quan when talking about a future or general situation.

So:

• Quan la meva mare es troba millor, torna a caminar...

can mean something like:

• When my mother feels better, she starts walking again...

This is very normal. English does something similar in many cases:

• When she feels better, she’ll...

Catalan may simply keep the present where English might use a future idea in the second part depending on context.

No. Here torna a does not mean physical return.

It means again.

So:

• torna a caminar = she walks again / she starts walking again

If you wanted to say she returns walking or she comes back on foot, that would be expressed differently.

So this is an important point: learn tornar a + infinitive as again, not as literal return.

Yes:

• Quan = when
• la meva mare = my mother
• es troba millor = feels better
• torna a caminar = walks again / starts walking again
• i = and
• ja no = no longer / not anymore
• li = to her
• fa mal = hurts
• el braç = the arm

A natural full translation would be:

• When my mother feels better, she starts walking again and her arm no longer hurts.

or

• When my mother is feeling better, she walks again and her arm doesn’t hurt anymore.

There are three especially useful patterns here:

1. trobar-se + adjective/adverbial expression

   • trobar-se bé = to feel well
   • trobar-se millor = to feel better

2. tornar a + infinitive

   • torna a caminar = walks again
   • torno a dir-ho = I say it again

3. indirect object pronoun + fer mal + body part

   • em fa mal el cap = my head hurts
   • li fa mal el braç = her arm hurts

If you remember those three patterns, this sentence becomes much easier to understand and reuse.