You are partially right. "Seu" (possessive pronoun for 3rd person) means "his" in both Brazilian or Portugal's Portuguese. However, since a lot of people in Brazil use "você" (3rd person) in place of "tu" (2nd person), you have to use correct pronoun: in this case "seu". Ex: 'You sell your car' can be written in these two ways: "Tu vendes teu carro." or "Você vende seu carro."
For a more detailed explanation, check my comment on this thread: https://www.duolingo.com/comment/1136527
I'm not an anglophone, but I think The cheese is from him denotes a transition, thus it would mean that someone received this cheese from him. It could indeed translate as this, but it's not a common translation, at least not with cheeses... But we say it often when referring to gifts, for example:
O presente é meu = The gift is mine / The gift is from me (I gave it)
Eu ganhei esse presente dele = I received this gift from him
"Yours" is not a plural form of "your". The former is a possessive pronoun (always used alone), while the latter a possessive adjective (always used before a noun phrase).
Possessive pronouns (most of them end in -s)
- The cheese is mine
- The cheese is your
- The cheese is hi
- The cheese is her
- The cheese is it
- The cheese is our
- The cheese is their
Possessive adjectives (most of them don't end in -s)
- It is my cheese
- It is your cheese
- It is hi
- It is her cheese
- It is it
- It is our cheese
- It is their cheese
Note that (only) "his" and "its" serve both roles, because they already end in -s.