Devo masticare lentamente quando il pane è duro.

Devo is the 1st person singular present tense of dovere.

• dovere = to have to / must
• devo = I have to / I must

So devo tells you that the speaker is talking about themself and expressing necessity or obligation.

A few related forms:

• devo = I must
• devi = you must
• deve = he/she/it must
• dobbiamo = we must

After a modal verb like dovere, Italian usually uses a second verb in the infinitive.

So the pattern is:

dovere + infinitive

Examples:

• Devo mangiare = I must eat
• Devi studiare = You must study
• Dobbiamo partire = We have to leave

That is why you get devo masticare, not a conjugated form like devo mastico.

Lentamente is an adverb, and it means slowly.

It modifies the verb masticare, telling you how the action is done.

In Italian, adverbs like this often come:

• after the infinitive: masticare lentamente
• or after a conjugated verb in other structures

So devo masticare lentamente is very natural.

You may also hear slightly different word orders in Italian depending on emphasis, but this version is straightforward and standard.

Quando means when, while se means if.

Here, quando il pane è duro expresses a situation understood as whenever/when the bread is hard, not a more hypothetical if the bread is hard.

So:

• quando = when / whenever
• se = if

In many real-life situations, either can be possible depending on nuance, but quando often sounds more like a general recurring condition.

Compare:

• Quando il pane è duro, devo masticare lentamente.
  = Whenever the bread is hard, I have to chew slowly.
• Se il pane è duro, devo masticare lentamente.
  = If the bread is hard, I have to chew slowly.

The second is more conditional; the first feels more like a regular fact.

Italian often uses the definite article to talk about things in a general sense, where English may use no article at all.

So il pane can mean:

• the bread in a specific context
• or bread in a general sense, depending on the sentence

This is very common in Italian.

Examples:

• Il pane è buono. = Bread is good.
• Il caffè mi piace. = I like coffee.
• La musica italiana è bella. = Italian music is beautiful.

So il pane è duro can naturally mean the bread is hard or bread is hard, depending on context.

È is the 3rd person singular of essere (to be), meaning is.

It needs the accent to distinguish it from e, which means and.

So:

• è = is
• e = and

This accent is very important in writing.

Example:

• Il pane è duro = The bread is hard
• Pane e formaggio = Bread and cheese

Also note that È is capitalized with the accent if it begins a sentence:

• È vero.

Duro is an adjective meaning hard.

Here it agrees with pane, which is:

• masculine
• singular

So the adjective must also be masculine singular:

• il pane duro = hard bread
• la carne dura = tough meat
• i biscotti duri = hard cookies
• le caramelle dure = hard candies

So duro is simply the correct agreement form for pane.

Yes. Italian often uses the present tense to talk about:

• general truths
• habits
• repeated situations
• things that are true whenever a certain condition happens

So Devo masticare lentamente quando il pane è duro does not have to mean only right now. It can also mean something like a general personal rule or a usual situation.

This is very normal in both Italian and English.

Yes, Italian word order is somewhat flexible, although some versions sound more neutral than others.

The original sentence is perfectly natural:

• Devo masticare lentamente quando il pane è duro.

You could also say:

• Quando il pane è duro, devo masticare lentamente.

This version puts the condition first and may sound slightly more emphatic or organized around the situation.

Both are correct. The original order is just a very standard, neutral way to say it.

A helpful approximate pronunciation is:

• masticare ≈ ma-stee-KA-re
• lentamente ≈ len-ta-MEN-te
• duro ≈ DOO-ro
• pane ≈ PA-ne
• devo ≈ DEH-vo

A couple of useful points:

• Italian usually pronounces vowels clearly.
• The stress in masticare falls on -ca-.
• The stress in lentamente falls on -men-.

If you want to sound more natural, keep the vowels clean and avoid reducing unstressed vowels too much, as English speakers often do.