Learn Hardcore Portuguese (Brazil): A técnica vai consertar a tomada da cozinha amanhã. - The technician is going to fix the kitchen outlet tomorrow.

In your sentence, because it’s followed by an action a person would do (vai consertar), it’s understood as the (female) technician. If you wanted to avoid any ambiguity, you could say A técnica de manutenção (the maintenance technician) or A técnica (mulher) in very explicit contexts.

Why is it A técnica and not O técnico?

Portuguese marks grammatical gender:

o técnico = the male technician
a técnica = the female technician

So the article a matches técnica. If you don’t know the person’s gender, in real life people often default to o técnico or use a more neutral wording like a pessoa técnica (less common) or just name the company/person.

What does vai consertar mean grammatically? Is it the future tense?

Yes—this is the common spoken future formed with ir (to go) + infinitive:

vai (present of ir) + consertar (infinitive) = is going to fix / will fix

It’s extremely common in Brazilian Portuguese and often preferred over the simple future (consertará), which can sound more formal.

Can I replace vai consertar with consertará?

Yes, and the meaning is basically the same:

A técnica vai consertar... = natural, everyday Brazilian Portuguese
A técnica consertará... = more formal, more “written” or official-sounding

In conversation in Brazil, vai consertar is usually the default.

Why is consertar in the infinitive?

Because it follows the structure ir + infinitive. After vai, the next verb stays in the infinitive:

vai consertar
vai trocar (is going to change/replace)
vai instalar (is going to install)

Only the first verb (ir) is conjugated.

What exactly is tomada here?

In Brazilian Portuguese, tomada commonly means an electrical outlet / wall socket / power point.
So consertar a tomada = to fix the outlet.

(Portuguese also has tomada meaning “taking” in other contexts, but the household/electric meaning is very common.)

Why is it a tomada da cozinha and not a tomada na cozinha?

Both are possible, but they emphasize different things:

a tomada da cozinha = the kitchen’s outlet / the outlet that belongs to the kitchen (identifying which outlet)
a tomada na cozinha = the outlet in the kitchen (location-focused)

When you’re distinguishing it from other outlets (bedroom, bathroom, etc.), da cozinha is very natural.

What does da mean?

da is a contraction of de + a:

de = of/from
a = the (feminine singular)

So da cozinha literally means of the kitchen.
Similarly:

do = de + o (of the)
dos = de + os
das = de + as

Could I say tomada de cozinha instead of tomada da cozinha?

You can, but it changes the nuance:

tomada da cozinha = the specific outlet that is in/assigned to that kitchen
tomada de cozinha = an outlet “of the kitchen type” (more generic/classifying), and it’s less common in this context

For a particular house/apartment, da cozinha is the most natural.

Where can amanhã go in the sentence?

Amanhã is flexible:

A técnica vai consertar a tomada da cozinha amanhã. (common)
A técnica vai consertar amanhã a tomada da cozinha. (possible, slightly more emphasis on time)
Amanhã, a técnica vai consertar a tomada da cozinha. (time-first emphasis)

All are correct; the first and third are the most natural.

Do I need to say ela (she) here?

No. Portuguese often drops subject pronouns because the verb ending already carries information:

A técnica vai consertar... is complete. You could say Ela vai consertar... if the technician is already known and you want to avoid repeating a técnica, but it’s optional.

How is técnica pronounced, and what’s the stress?

técnica has stress on the first syllable because of the accent mark: TÉC-ni-ca.
In Brazilian Portuguese, it sounds roughly like TEK-nee-kah (with a clear é sound in the stressed syllable).