Quando o computador trava, a Júlia fica nervosa e chama a técnica.

O is the masculine singular definite article, meaning the.

So o computador = the computer.

Portuguese uses definite articles more often than English does, so it is very normal to say o computador where English might sometimes just say computer in a general statement.

Here, trava comes from the verb travar and means freezes, hangs, or stops responding.

In other contexts, travar can have other meanings, such as to lock, to jam, or to become stuck. But with computers, o computador trava is a very common way to say that the computer freezes.

The present tense here expresses something habitual or generally true.

So this sentence does not describe one single event only. It means something like:

• whenever this happens
• every time this happens
• this is the usual reaction

In Portuguese, with quando meaning when/whenever, the present tense is often used for repeated situations:

• Quando chove, eu fico em casa.
• Quando o celular toca, ela atende.

The comma separates the quando clause from the main clause:

• Quando o computador trava, = introductory time clause
• a Júlia fica nervosa e chama a técnica. = main clause

This is very common in Portuguese, and it is also natural in English when a when clause comes first.

If the order changes, the comma may disappear:

• A Júlia fica nervosa e chama a técnica quando o computador trava.

In Brazilian Portuguese, it is very common to use a definite article before a person's name:

• a Júlia
• o Paulo
• a Marina

This does not change the basic meaning. It still just means Júlia.

Whether the article is used can depend on region, style, and personal habit. In many parts of Brazil, using the article sounds very natural in everyday speech.

Ficar often means to become or to get, while ser means to be in a more permanent or defining way.

So:

• fica nervosa = gets nervous / becomes nervous
• é nervosa = is a nervous person by nature

In this sentence, Júlia’s nervousness is a reaction to the computer freezing, so fica nervosa is the right choice.

Because nervosa agrees with Júlia, who is feminine.

In Portuguese, adjectives usually agree in gender and number with the noun they describe:

• o menino nervoso
• a menina nervosa
• os meninos nervosos
• as meninas nervosas

So with Júlia, it must be nervosa.

Chama is from the verb chamar.

Here it most likely means calls in the sense of contacts, calls for, or summons the technician.

Depending on context, chamar can mean:

• to call someone by name
• to call out
• to phone
• to call for / summon

In this sentence, since the topic is a computer problem, chama a técnica probably means she contacts the technician for help.

Here técnica is a noun meaning female technician.

The article a can be understood as the, so a técnica means the technician.

It also tells you that the technician is female. If it were male, it would be:

• o técnico

This is different from English, where technician does not usually show gender.

Yes. Técnica can be either:

• a noun: female technician
• an adjective: technical (feminine form)

Examples:

• Ela é técnica de informática. = She is an IT technician.
• linguagem técnica = technical language

In your sentence, a técnica is clearly a noun because it has an article and refers to a person.

Because Portuguese often leaves out subject pronouns when the subject is already clear.

In this sentence, the subject is already a Júlia, so there is no need to repeat it:

• a Júlia fica nervosa e chama a técnica

That is more natural than repeating:

• a Júlia fica nervosa e ela chama a técnica

Portuguese does this a lot, especially when the verb form makes the subject easy to understand.

Yes. In a sentence like this, quando can often be understood as when or whenever, depending on context.

Because the verbs are in the present tense and the sentence sounds like a repeated situation, English would often naturally translate it as:

• Whenever the computer freezes, Júlia gets nervous and calls the technician.

So quando does not always point to one single future or past event. It can also describe a regular pattern.

Yes, but the meaning changes.

• a técnica = the technician (a specific or known technician)
• uma técnica = a technician (not specific)

So:

• chama a técnica suggests there is a particular technician they already know or normally contact
• chama uma técnica would suggest calling any female technician

Yes. The sentence has one subject, a Júlia, and two coordinated actions:

• fica nervosa
• chama a técnica

So the structure is:

• Quando o computador trava,
• a Júlia
  • fica nervosa
    • e chama a técnica

In English terms, it is like: When the computer freezes, Júlia gets nervous and calls the technician.

Both verbs describe what Júlia does in that situation.