Words and phrases:
線上 - xiànshàng - online
確定 - quèdìng - certain

才 - cái - Very roughly translated as "only" -- This word indicates a condition that must be fulfilled or a number or amount that is less or later than expected, among other things. It's best learned through context:

• Example 1: 西瓜好便宜！一顆才100塊！
  • Xīguā hǎo piányí! Yī kē cái 100 kuài!
  • Watermelons are so cheap! Only 100 NT per 顆 (kē - a measure word for round things).
• Example 2: 他要打給我，我才會跟他說
  • Tā yào dǎ gěi wǒ, wǒ cái huì gēn tā shuō
  • Only if he calls me will I tell him.
• Example 3: 我昨天才知道你結婚了！
  • Wǒ zuótiān cái zhīdào nǐ jiéhūnle!
  • I only knew yesterday that you got married!
• Example 4: 我才不相信！
  • Wǒ cái bù xiāngxìn!
  • I don't believe you! (the 才 in this case gives emphasis)

These examples in no way cover the range of ways 才 is used. Again, it's best learned through context by understanding the sense of the whole phrase. Also worth noting that it has a counterpart, 就 (jiù) which very roughly translates as "just" and indicates conditions that are easier than expected, or numbers or amounts that are more than expected or earlier than expected.

1. 你現在要去哪？
   1. Nǐ xiànzài yào qù nǎ?
   2. Where are you going now?
2. 我要去買禮物
   1. Wǒ yào qù mǎi lǐwù
   2. I'm going to buy presents.
3. 送給女朋友嗎？
   1. sòng gěi nǚ péngyǒu ma?
   2. To give to your girlfriend?
4. 不是，要送給我的家人
   1. Bùshì, yào sòng gěi wǒ de jiārén
   2. No, to give to my family.
5. 是哦！你要買什麼？
   1. shì ó! Nǐ yāomǎi shénme?
   2. Oh! What are you going to buy?
6. 我還不知道，現在很多店都關了！
   1. Wǒ hái bù zhīdào, xiànzài hěnduō diàn dōu guānle!
   2. I don't know yet, a lot of shops are closed now.
7. 線上買呢？
   1. Xiànshàng mǎi ne?
   2. What about buying online?
8. 可是我覺得我要看到、摸到才能確定
   1. Kěshì wǒ juédé wǒ yào kàn dào, mō dào cáinéng quèdìng
   2. But I have to see them and feel them to really be sure.
9. 也是... 送茶葉呢？
   1. yěshì... Sòng cháyè ne?
   2. True that... what about giving tea?
10. 他們不太懂喝茶
    1. Tāmen bù tài dǒng hē chá
    2. They don't really appreciate tea.
11. 那... 鳳梨酥呢？
    1. nà... Fènglí sū ne?
    2. Then... how about pineapple cake?
12. 已經送過太多次了
    1. Yǐjīng sòngguò tài duō cìle
    2. I've already given it too many times.
13. 是哦... 買禮物真的很不簡單！
    1. shì ó... Mǎi lǐwù zhēn de hěn bù jiǎndān!
    2. Oh... buying presents really isn't easy!
14. 你看我買的貼紙！
    1. Nǐ kàn wǒ mǎi de tiēzhǐ!
    2. Look at the stickers I bought!
15. 狗狗的貼紙好可愛！
    1. Gǒu gǒu de tiēzhǐ hǎo kě'ài!
    2. The dog stickers are so cute!
16. 還有這個貼紙
    1. Hái yǒu zhège tiēzhǐ
    2. There's also this sticker.
17. 禁止吸煙？
    1. jìnzhǐ xīyān?
    2. Smoking prohibited?