Paul est très poli avec sa colocataire, mais sa sœur peut être un peu impolie.

Poli agrees in gender and number with the subject Paul, who is male.
French adjectives usually agree with the noun they describe:

• masculine singular: poli
• feminine singular: polie
• masculine plural: polis
• feminine plural: polies

Since Paul is masculine singular, you use poli.

Here the adjective describes sa sœur, which is feminine singular (une sœur).
So the adjective must also be feminine singular: impolie (with -e at the end), not impoli.

In French, mon / ma / mes, ton / ta / tes, son / sa / ses agree with the thing possessed, not with the owner.

• sa colocataire → colocataire is feminine here
• sa sœur → sœur is feminine

So we use sa (feminine singular) both times, even though the owner (Paul) is male.

Colocataire is an epicene noun: the spelling is the same for masculine and feminine.
You see the gender from the determiner:

• son colocataire = his/her male roommate
• sa colocataire = his/her female roommate

Here it’s sa colocataire, so the roommate is female.

Avec literally means with and is very common when talking about how you behave with someone.

Envers is closer to towards in English and is a bit more formal or written style. You could say poli envers sa colocataire, but poli avec sa colocataire is more neutral and natural in everyday speech.

• Peut être (two words) = can be (verb peut

  • infinitive être)
  • sa sœur peut être un peu impolie = his sister can be a bit impolite.

• Peut-être (with hyphen) = maybe / perhaps (an adverb)

  • Peut-être sa sœur est un peu impolie = Maybe his sister is a bit impolite.

They are pronounced almost the same but have different roles and spellings.

Yes, sa sœur est un peu impolie is grammatically correct.

• peut être un peu impolie = can be a bit impolite → it’s not always; sometimes she behaves that way.
• est un peu impolie = is a bit impolite → a more constant trait of character.

So peut être softens the statement and makes it less absolute.

You normally use a possessive (sa, son, ses) instead of a definite article (le, la, les) when you say someone’s [family member/body part/etc.]:

• sa sœur = his/her sister
• la sœur de Paul = Paul’s sister

Both are correct, but sa sœur is shorter and more natural when the possessor is already clear from the context (here, Paul).

No, you can’t move them like that. In French, adverbs like très and un peu usually go directly before the adjective:

• est très poli (not est poli très)
• un peu impolie (not impolie un peu in this short phrase)

The neutral pattern is: verb + adverb + adjective or adverb + adjective.

They are very close in meaning and often interchangeable:

• impoli(e) = impolite, not polite
• malpoli(e) = also impolite, literally badly polite

Malpoli can sound a bit stronger or more informal in some contexts, but both are common for describing rude or badly mannered behavior.

Mais = but and is the standard conjunction to introduce a contrast between two clauses: poli… mais… impolie.

You could say …avec sa colocataire, par contre sa sœur…, but par contre works more like on the other hand and is often placed after a pause. Mais is simpler and more neutral in this sentence.

There is usually one liaison:

• Paul est très poli → /pɔl‿ɛ tʁɛ pɔli/
  
  • Liaison between Paul and est: Paul est → pɔl‿ɛ (the final l of Paul is linked to est).
  • No liaison between très and poli: you say trè poli, not trè-z-poli.

So you link Paul and est, but not très and poli.

Yes, sa coloc is a common informal shortening of sa colocataire, especially in speech and casual writing.

• sa colocataire → neutral, standard
• sa coloc → colloquial, familiar

Both refer to the roommate; choose depending on how informal you want to sound.