Même après le malentendu, son comportement reste calme et poli.

Here même means even. It strengthens the contrast:

• Après le malentendu = after the misunderstanding
• Même après le malentendu = even after the misunderstanding

So it suggests that, despite something potentially upsetting happening, the behavior still stays calm and polite.

Le is the definite article, so it points to a specific misunderstanding that the speaker and listener already know about, or that has already been mentioned.

• après le malentendu = after the misunderstanding
• après un malentendu = after a misunderstanding

Using le makes the situation sound more specific and grounded in context.

Because comportement is a masculine singular noun, and the possessive adjective has to agree with the noun being possessed, not with the person who owns it.

So:

• son comportement = his behavior / her behavior

This is important for English speakers: son does not automatically mean the owner is male. It can refer to his, her, or sometimes its, depending on context.

It could mean his or her. French possessive adjectives usually do not tell you the gender of the owner; they tell you the gender and number of the noun that follows.

Since comportement is masculine singular, French uses son no matter whether the person is male or female.

So son comportement can mean:

• his behavior
• her behavior

You need context to know which one.

Reste comes from rester, meaning to remain or to stay. It shows continuity: the behavior continues to be calm and polite, even after the misunderstanding.

• son comportement est calme et poli = his/her behavior is calm and polite
• son comportement reste calme et poli = his/her behavior remains calm and polite

So reste is more expressive here because it highlights that the misunderstanding did not change the behavior.

Because they describe comportement, which is masculine singular.

In French, adjectives usually agree with the noun they describe:

• masculine singular: calme, poli
• feminine singular: calme, polie
• masculine plural: calmes, polis
• feminine plural: calmes, polies

Since comportement is one thing and masculine, calme et poli is the correct form.

Because calme and poli are predicate adjectives after the verb rester. In this structure, French normally does not use an article.

This is similar to English:

• Il est calme.
• Elle reste polie.

Not:

• Il est le calme.
• Elle reste la polie.

So reste calme et poli is the normal pattern.

Yes. French allows some flexibility here.

You could also say:

Son comportement reste calme et poli, même après le malentendu.

Both versions are natural, but the emphasis changes slightly:

• Même après le malentendu, ... puts the contrast first
• Son comportement reste calme et poli, même après le malentendu. starts with the main statement and adds the contrast afterward

The original version sounds a bit more focused on despite the misunderstanding.

Yes. Malentendu means misunderstanding.

It is related to the idea of hearing or understanding badly:

• mal- = badly, wrongly
• entendre = to hear, sometimes to understand depending on context

So malentendu is a useful word to remember as something like a wrong understanding.

Yes, it is natural, but it sounds a little neutral or formal. Comportement means behavior or conduct.

Depending on context, French could also use other wording, such as:

• Il/Elle reste calme et poli(e).
• Son attitude reste calme et polie.

The original sentence is perfectly correct, but comportement focuses on the person’s outward behavior in a slightly more descriptive way.

Here poli clearly means polite because it describes comportement.

In other contexts, poli can also mean polished, especially for objects or surfaces. But with a person’s behavior, the meaning is naturally polite.

So in this sentence:

• calme = calm
• poli = polite

It is not absolutely required in every case, but it is very natural here. The phrase Même après le malentendu is an introductory element, and the comma helps separate it from the main clause.

So the comma improves readability and rhythm:

• Même après le malentendu, son comportement reste calme et poli.

Without the comma, the sentence would still be understandable, but the written style is smoother with it.