Conviene masticar despacio cuando comes tan deprisa.

Conviene is a very common Spanish way to say that something is advisable, suitable, or a good idea.

In this sentence, conviene + infinitive means it’s advisable to... or it’s a good idea to...

So:

Conviene masticar despacio = It’s advisable to chew slowly

It is often used impersonally, without saying exactly who it is advisable for. English often uses it’s best, it’s advisable, or you should in similar situations.

Because after conviene, Spanish often uses an infinitive to talk about a general action.

Pattern: conviene + infinitive

Examples:

• Conviene descansar. = It’s advisable to rest.
• Conviene llegar pronto. = It’s a good idea to arrive early.
• Conviene masticar despacio. = It’s advisable to chew slowly.

If Spanish wants to name a specific person, it can also use: conviene que + subjunctive

For example: Conviene que mastiques despacio. = It’s advisable that you chew slowly.

Because cuando comes refers to something habitual, repeated, or real: when you eat so fast / whenever you eat so fast.

Spanish often uses the present indicative after cuando for regular or actual situations:

• Cuando llego tarde, llamo.
• Cuando comes tan deprisa, te sienta mal.

You would use cuando comas if you were referring to a future event:

• Cuando comas, llámame. = When you eat / when you’re about to eat later, call me.

So here:

• cuando comes = whenever you eat like that / in situations that really happen
• cuando comas = when you eat in the future

Comes is the tú form of comer, so the speaker is addressing someone directly: when you eat so fast.

Spanish often leaves out the subject pronoun, so tú comes becomes simply comes.

This makes the sentence feel like advice given to one person.

If you wanted to make it more general, Spanish could say something like:

• Conviene masticar despacio cuando se come tan deprisa.

That would sound more like: It’s advisable to chew slowly when one eats so fast / when people eat so fast

Both can mean slowly, but despacio is more common and more natural in everyday speech.

• despacio = slowly, at a slow pace
• lentamente = slowly, but often sounds a bit more formal or descriptive

In advice like this, masticar despacio sounds very natural.

Compare:

• Habla despacio. = Speak slowly.
• Respira despacio. = Breathe slowly.

You could say masticar lentamente, but masticar despacio is more idiomatic in normal conversation.

Both can mean quickly or fast, but deprisa is especially common in everyday Spanish, including in Spain.

• deprisa = quickly, in a hurry, fast
• rápidamente = quickly, rapidly, a bit more neutral or formal

In spoken Spanish, deprisa often sounds more natural:

• Hablas muy deprisa.
• No comas tan deprisa.

So comes tan deprisa is a very natural everyday way to say you eat so fast.

Tan means so, while muy means very.

So:

• muy deprisa = very fast
• tan deprisa = so fast

In this sentence, tan deprisa often implies to such a fast degree, which fits well with the advice that follows.

Compare:

• Hablas muy deprisa. = You speak very fast.
• Hablas tan deprisa que no te entiendo. = You speak so fast that I can’t understand you.

Here, even without a full que... clause, tan deprisa still works naturally.

Yes. Spanish word order is flexible here.

The original: Conviene masticar despacio cuando comes tan deprisa.

You could also say: Cuando comes tan deprisa, conviene masticar despacio.

Both are correct. The difference is mainly one of emphasis:

• starting with Conviene... highlights the advice
• starting with Cuando comes tan deprisa... highlights the situation first

The original version sounds very natural.

Yes, but conviene is shorter and more idiomatic in many everyday contexts.

Compare:

• Conviene masticar despacio.
• Es conveniente masticar despacio.

Both are correct, but conviene often sounds more natural and direct in ordinary advice.

Es conveniente can sound a little more formal or explanatory.

Yes. Masticar is the standard verb for to chew.

Examples:

• Tienes que masticar bien. = You have to chew well.
• Mastica despacio. = Chew slowly.

In everyday speech, it is completely normal. In this sentence, it is exactly the right verb.

It would be understood everywhere, but it has a slightly European Spanish feel because deprisa is especially common in Spain.

That said, speakers in many Spanish-speaking countries also use deprisa, and the whole sentence is perfectly understandable across the Spanish-speaking world.

A small regional variation might be:

• Conviene masticar despacio cuando comes tan rápido.

But the original sentence is fully natural and standard.