Si no tens la resposta, fes una pregunta.

Si means if. It introduces a condition:

• Si no tens la resposta = If you don’t have the answer
• fes una pregunta = ask a question

So the whole sentence follows the common pattern if X, do Y.

Tens is the 2nd person singular form of tenir (to have) in the present tense.

• jo tinc = I have
• tu tens = you have
• ell/ella té = he/she has

So no tens means you don’t have.

Catalan usually forms negation by putting no before the verb:

• tens = you have
• no tens = you don’t have

La resposta means the answer.

Catalan often uses the definite article where English also does:

• la resposta = the answer
• una pregunta = a question

Here, la resposta refers to a specific answer, while una pregunta means any question.

Fes is the tu imperative form of fer, which usually means to do or to make. In Catalan, fer una pregunta is the normal way to say to ask a question.

So:

• fer una pregunta = to ask a question
• fes una pregunta = ask a question

This is a command or instruction directed to one person.

Yes. It comes from the irregular verb fer.

Some useful forms are:

• fer = to do / to make
• fa = he/she does
• fem = we do
• fes = do! / make! / ask! (to one person)

So fes is not built in a fully regular way. It is a form you should memorize.

Catalan often uses fer in expressions where English uses a more specific verb. One very common expression is:

• fer una pregunta = to ask a question

This is completely natural Catalan. English speakers may expect a direct equivalent of ask, but here Catalan uses the expression with fer.

The comma separates the conditional clause from the main instruction:

• Si no tens la resposta, = If you don’t have the answer,
• fes una pregunta. = ask a question.

This is very similar to English punctuation in a sentence like:

• If you don’t know the answer, ask a question.

It is informal singular, because it uses:

• tens = you have (tu form)
• fes = do/ask! (tu imperative)

If you wanted a more formal version, you would use the vostè form instead.

For vosaltres (informal plural), it would be:

• Si no teniu la resposta, feu una pregunta.

Changes:

• teniu = you all have
• feu = do/make/ask! (plural imperative of fer)

No. Even though fer often means make or do, in fer una pregunta the natural translation is ask a question.

So you should understand:

• fes una pregunta = ask a question

not literally make a question in normal English.

Una pregunta means a question, not the question. The idea is not about one specific question already known to both people. It means:

• ask some question
• ask a question if you need to

That is why the indefinite article una is used.

The structure is:

• Si
  • negative clause + comma + imperative clause

More specifically:

• Si = if
• no tens la resposta = you don’t have the answer
• fes una pregunta = ask a question

This word order is very natural in Catalan and closely matches English:

• If you don’t have the answer, ask a question.