No només l'entrevistador sinó també el candidat fa preguntes.

It is a correlative structure: the first part introduces one element, and the second part adds another.

• no només X sinó també Y
• not only X but also Y

Here, X is l'entrevistador and Y is el candidat.

Because sinó is the normal conjunction in this kind of structure after a negative element such as no només. It is not just a general but.

• però = ordinary but
• sinó = used after negation to correct, replace, or add in patterns like no només ... sinó també ...

So sinó també is the natural choice here.

Because sinó també is followed by a noun phrase, not a full new clause.

Here we have:

• sinó també el candidat = still just the second coordinated noun phrase

You use sinó que when what follows is a full clause with its own conjugated verb, for example:

• No només pregunta, sinó que també respon.

So in your sentence, sinó també is enough.

Because the masculine singular article el becomes l' before a word beginning with a vowel or silent h.

• el + entrevistador → l'entrevistador

This is standard Catalan elision.

Because candidat begins with a consonant, so the article stays el.

• before a vowel: l'entrevistador
• before a consonant: el candidat

Also, Catalan normally keeps the definite article with specific nouns like these, just as English does in the interviewer and the candidate.

Fa is the 3rd person singular present form of fer.

• fer = to do / to make
• fa = he/she/it does / makes

Catalan very often uses fer una pregunta or fer preguntes for the idea of asking a question / asking questions.

Catalan can use preguntar, but fer una pregunta / fer preguntes is also very common and idiomatic.

So these are both possible kinds of expressions:

• El candidat fa preguntes.
• El candidat pregunta coses.

The sentence you have uses the very common noun-based expression fer preguntes.

Because the sentence is talking about asking questions in general, not one single question.

• fa una pregunta = asks one question
• fa preguntes = asks questions

So the plural is about the object, not the subject.

That is a very reasonable question. In real Catalan, this kind of structure can show some variation.

Many learners would expect:

• No només l'entrevistador sinó també el candidat fan preguntes.

And that plural agreement is very understandable, because the meaning is clearly plural.

Your sentence has singular fa, which can also appear in no només ... sinó també ... structures. If you are producing Catalan yourself, fan is often the safer choice when you want full plural agreement, but you may still encounter singular agreement like fa in real usage.

They help show the stressed syllable and, in Catalan, often the vowel quality as well.

These words are stressed on the last syllable:

• no-més
• si-nó
• tam-bé

So the accents are not optional decoration; they are part of the correct spelling.

Yes, but the given order is the most straightforward and neutral one. The two-part pattern no només ... sinó també ... should stay clearly matched.

In a short sentence like this, commas are often omitted. In a longer sentence, a writer might add commas for readability:

• No només l'entrevistador, sinó també el candidat, fa/fan preguntes.

So the version without commas is perfectly normal.