Quan faig servir l'ordinador, no miro el telèfon.

Because fer servir is a very common Catalan expression meaning to use.

• fer = to do / to make
• servir = to serve
• but together, fer servir = to use

So:

• faig servir = I use
• fas servir = you use
• fa servir = he/she uses

You may also see utilitzar, which is a more direct equivalent of to use, but fer servir is extremely natural in everyday Catalan.

Because fer is the infinitive, meaning to do / to make. In the sentence, the verb has to be conjugated:

• fer = to do
• faig = I do / I make

Since the subject is understood as I, Catalan uses faig.

So:

• Quan faig servir... = When I use...

not

• Quan fer servir... ❌

Catalan often drops subject pronouns when they are clear from the verb ending.

Here:

• faig already tells you the subject is I
• miro also tells you the subject is I

So jo is not necessary.

You could say:

• Quan jo faig servir l'ordinador, no miro el telèfon.

But that sounds more emphatic, as if you are stressing I specifically.

In normal speech, Catalan usually prefers:

• Quan faig servir l'ordinador, no miro el telèfon.

Because el becomes l' before a vowel sound.

• el llibre = the book
• el telèfon = the phone
• l'ordinador = the computer

This is called elision. It makes pronunciation smoother.

So:

• el + ordinador → l'ordinador

Catalan uses definite articles very naturally before nouns, including ordinary objects like phone and computer.

Here el telèfon simply means the phone, but in context it often corresponds to what English speakers would naturally understand as my phone.

Catalan does this a lot more than English. The sentence is talking about a familiar, specific object in context, so el telèfon sounds perfectly natural.

In Catalan, no usually goes directly before the conjugated verb.

So:

• no miro = I do not look / I do not check

This is the normal way to make a sentence negative.

Examples:

• No parlo català. = I don’t speak Catalan.
• No menjo carn. = I don’t eat meat.

So:

• no miro el telèfon = I don’t look at the phone

They are both in the present indicative.

• faig = I do / I use
• miro = I look

In this sentence, the present tense expresses a habitual action or general behavior:

• When I use the computer, I don’t look at the phone.

This is the same kind of use as English present simple in habitual statements.

Quan means when, and it works well here for a general repeated situation:

• Quan faig servir l'ordinador... = When I use the computer...

A learner might wonder about mentre, which means while.

• Quan focuses on the situation/time when something happens.
• mentre emphasizes that two things happen at the same time.

So you could also say:

• Mentre faig servir l'ordinador, no miro el telèfon.

That would mean something more like:

• While I’m using the computer, I don’t look at the phone.

Both can work, but quan is very natural here.

Because mirar means to look at, and in many contexts Catalan uses it where English might say look at, watch, or even check.

So:

• miro el telèfon literally = I look at the phone

But in natural English, depending on context, it may also mean:

• I check my phone

That is why mirar is a very useful everyday verb.

Yes, you could.

• Quan faig servir l'ordinador...
• Quan utilitzo l'ordinador...

Both are grammatical and understandable.

The difference is mostly one of style:

• fer servir = very common and everyday
• utilitzar = also correct, sometimes a bit more formal or technical

In ordinary speech, many speakers would prefer fer servir.

The comma is natural and helpful because the sentence begins with a subordinate clause:

• Quan faig servir l'ordinador, no miro el telèfon.

This is similar to English, where a comma is often used after an opening when clause.

In informal writing, some people may omit it, but using the comma here is a good choice and makes the sentence easier to read.

Yes. If el telèfon is already known from context, Catalan can replace it with the direct object pronoun el:

• No miro el telèfon. = I don’t look at the phone.
• No el miro. = I don’t look at it.

Notice that the pronoun goes before the verb:

• el miro = I look at it
• no el miro = I don’t look at it

That word order is very important in Catalan.

Yes, faig can look strange to English speakers.

In standard Catalan, it is pronounced roughly like fatch or faj depending on accent and how exact you want to be. The final sound is not pronounced like English g in go.

The important thing for learners is:

• it is the I form of fer
• faig servir is a very common chunk, so it is worth learning as a whole expression

If you remember faig servir as one unit meaning I use, that often helps more than analyzing every sound at first.