Laura dice che la cena riesce meglio quando nessuno ha fretta.

Here riesce meglio means something like turns out better, comes out better, or goes better.

The verb riuscire often means:

• to succeed
• to manage to do something
• to turn out well

In this sentence, it is not about a person succeeding. It is about the result of the dinner. So la cena riesce meglio means the dinner turns out better.

Because riuscire adds the idea of the final outcome.

Compare:

• La cena è buona = the dinner is good
• La cena viene bene = the dinner comes out well
• La cena riesce meglio = the dinner turns out better / is more successful

So riuscire suggests that the dinner is an event or meal whose overall result is better under certain conditions.

Italian often uses the definite article more than English does.

So:

• la cena = dinner / the dinner

In English, we often say just dinner in a general sense. In Italian, la cena is very natural here, even when speaking generally.

This does not necessarily mean one specific dinner. It can mean dinner as an occasion, in a general sense.

Because dire che normally takes the indicative when you are simply reporting what someone says as a statement.

So:

• Laura dice che la cena riesce meglio... = Laura says that dinner turns out better...

The subjunctive is more likely after expressions of doubt, emotion, uncertainty, or personal judgment, for example:

• Dubito che...
• È possibile che...
• Penso che... sometimes, depending on style and certainty

But after dice che, the indicative is the normal choice.

Because nessuno is grammatically singular.

So Italian says:

• nessuno ha fretta = no one is in a hurry

Even though it refers to many possible people, the grammar treats nessuno as singular, just like English no one is.

That is why the verb is:

• ha, not hanno

Yes, this is an idiomatic expression.

Avere fretta means:

• to be in a hurry
• to be rushed

Italian uses avere here, not essere.

So:

• ho fretta = I am in a hurry
• hai fretta = you are in a hurry
• nessuno ha fretta = no one is in a hurry

This is just one of those expressions that must be learned as a whole.

Because the standard expression is simply avere fretta, without an article.

Many Italian expressions with avere work this way:

• avere fame = to be hungry
• avere sete = to be thirsty
• avere paura = to be afraid
• avere fretta = to be in a hurry

So ha fretta is the normal fixed expression.

Meglio modifies the verb phrase riesce.

It tells us how the dinner turns out:

• riesce meglio = turns out better

So meglio is functioning as an adverb here, not an adjective.

A useful comparison:

• buono = good
• bene = well
• meglio = better

You do not say più bene in standard Italian. The correct comparative form is meglio.

Here it can be understood as when in a general sense, very close to whenever.

The sentence expresses a general truth:

• dinner turns out better when no one is in a hurry

So it is not necessarily about one single occasion. It means in those situations where nobody is rushed, dinner goes better.

Yes. Italian word order is flexible, as long as the meaning stays clear.

For example, you could also say:

• Laura dice che quando nessuno ha fretta, la cena riesce meglio.

That version puts more emphasis on the condition quando nessuno ha fretta.

The original sentence is perfectly natural, and so is the reordered version.

Because the sentence expresses a general statement or habitual truth.

• Laura dice = Laura says
• la cena riesce meglio = dinner turns out better
• quando nessuno ha fretta = when no one is in a hurry

Italian often uses the present tense for general truths, just like English:

• Water boils at 100 degrees
• Dinner turns out better when no one is in a hurry

So the present tense is exactly what you would expect here.

Yes, that is possible, but it sounds more marked or stylistic.

• quando nessuno ha fretta is the most neutral and natural order
• quando non ha fretta nessuno puts extra emphasis on nessuno

Also notice that when nessuno comes after the verb, Italian often uses non as well:

• Non è venuto nessuno = nobody came

In your sentence, the straightforward version is definitely quando nessuno ha fretta.

No. Here che is a conjunction meaning that.

It connects:

• Laura dice with
• la cena riesce meglio quando nessuno ha fretta

So:

• dice che... = says that...

It is not replacing a noun, so it is not a relative pronoun in this sentence.