i chinguga gwiyeowoyo.

In Korean, -가 marks the grammatical subject—what or who performs the action or possesses the property—while -는 marks the topic—what you’re talking about.

• 이 친구가 귀여워요 with -가 focuses on “this friend” as the one who is cute (e.g. among others, this one stands out).
• 이 친구는 귀여워요 with -는 would mean “As for this friend, (he/she) is cute,” often implying contrast or change of subject in the conversation.

The ending -요 is the polite informal declarative ending. It:

• Makes your statement polite enough for strangers or casual acquaintances.
• Is warmer and more conversational than the formal -습니다 ending.
• Is more polite than the plain ending (귀여워), which you’d use with very close friends or younger people.

귀엽다 belongs to the ㅂ-irregular verbs. Conjugation steps:

1. Drop -다 ⇒ 귀엽-
2. The final ㅂ in the stem changes to 우 before a vowel ⇒ 귀여우-
3. Add the polite ending -요 ⇒ 귀여워요

This is why the ㅂ disappears and you hear ’귀여우’ instead of ’귀엽우’.

Korean follows Subject–(Object)–Verb/Predicate order. With an adjective predicate there’s no object, so:

1. Subject: 이 친구가
2. Predicate: 귀여워요

In English you say “This friend is cute” (Subject–Verb–Complement), but in Korean the predicate (귀여워요) always comes last.

Simply use rising intonation or add a question mark in writing:

• 이 친구가 귀여워요?
  If you want an even more formally polite question, you could say 이 친구가 귀여우세요? when showing extra respect to the friend.

Phonetically it’s roughly:

• 이 [i]
• 친구가 [tɕʰinɡuɡa]
• 귀여워요 [ɡwi.jʌ.wʌ.jo]

All together: [i tɕʰinɡuɡa ɡwijʌwʌjo]. In fast, natural speech you might link words so it flows like “이친구가귀여워요.”