Every Furby is born speaking only Furbish, then slowly learns English as you love on it. Below is an expanded dictionary drawn from the Fandom language article, paired with the classic 1998 manual entries.
Classic Manual Phrases
Doo? — Hi / Hello
Doo-doo — How are you? / Baby
Wee-tah-kah-loo-loo — Tell me a story
Wee-tah-kah-wee-loo — Go to sleep
Eh-oh — Oh!
Oo-tah — Eat
Ah-ay — Yes
Noo-loo — No
Bo — Bored
Dee-oo — Duty / Need to poop
Oo-boo — Scared
Kah — Cat
May-may — Mommy
Pa-pa — Daddy
Bay-bee — Baby
Dah — Dance
Nuk-nuk — Nuzzle
Sing? — Sing?
Way-loh-moo — What's that?
Koh-koh — Hold me
Expanded Dictionary
Ah — Yes / Yeah
Aye-ay — Happy / Excited
Buh-kah — Because
Dee-dah — Again / Repeat
Eee — Good / Nice
Hee — Laugh / Fun
Kah-loo — I love you / Affection
Koh-ay — Question / Huh?
Mee — Me / I
Nay — No / Nah
Oo-bah — Wow / Whoa
Oo-way — I want / Gimme
Ray-ray — Happy / Yay
Tee — Thanks / Please
Too — Too / Also
Wah — Sad / Upset
Yay — Yes / Yay
Sources: Furbish (language) — Furby Fandom; 1998 Manual Copy — Furby Fandom.