Learn Italian: La casa non è grande.

In Italian, the negative word non always goes directly before the verb it negates. While in English we say "is not" (verb + not), Italian does the opposite: non è (not + is).

Because casa is a feminine noun, shouldn't the adjective be granda?

Some Italian adjectives end in "-o" for masculine and "-a" for feminine, but grande belongs to a different group of adjectives that end in "-e" in the singular. These adjectives use the exact same form for both masculine and feminine nouns.

Why is there an accent mark on è?

The accent mark distinguishes è (meaning "is") from the word e (meaning "and"). Without the accent, the sentence would confusingly mean "The house not and big."