* "Us" is a pronoun, but it's not indefinite. It's a personal pronoun, specifically an object pronoun, because it's the object of a verb or preposition.
* "Several" is not a pronoun at all. It's a determiner, a word that comes before a noun to specify quantity.
Here's why "us" is not indefinite:
* Indefinite pronouns refer to non-specific people or things. Examples include: someone, anyone, everyone, nobody, something, anything, everything, nothing.
* Personal pronouns refer to specific people or things. They change depending on the person, number, and gender: I, you, he, she, it, we, you, they.
Let me know if you have any other pronoun questions!