Learn Polish: Znam wasze sprawy. - I know your matters.

Wasze is the plural "your" (like "y'all's"), coming from the pronoun wy (you, plural). If you were talking to just one person, you would use twoje instead.

What case is wasze sprawy in?

It is in the Accusative case because it is the direct object of the verb znać (to know). For non-masculine-personal nouns like sprawy (matters), the Accusative plural looks exactly the same as the Nominative plural!

Why does wasze end in -e?

Possessive pronouns have to match the noun they describe. Sprawy is a non-masculine-personal plural noun. In both the Nominative and Accusative cases, possessive pronouns for this group end in -e (like moje, twoje, nasze, and wasze).

Why does the verb znam mean "I know" here, rather than wiem?

In Polish, znać (here: znam) is used when you know a noun—a person, a place, or a thing (like sprawy). You use wiedzieć (to know) when you know a fact, usually followed by a full clause starting with "that", "what", or "where".