On a street in campus, Sun Dawei meets Li Mei holding many things that she bought from the supermarket.

Dialogue One

lǐ  méi  nǐ wèi shén  me mǎi le zhè me  duō  dōng xi
李 梅, 你 为  什  么  买  了  这  么  多  东  西?
Li Mei, why did you buy so many things?
wèi  wǒ  de shēng  ri  jù  huì zuò zhǔn  bèi
为  我  的  生  日 聚 会  做  准  备。
zhōu sì  nǐ néng  lái cān jiā wǒ de  shēng ri  jù  huì ma
周  四 你  能  来  参  加 我  的  生  日 聚 会  吗?
To prepare for my birthday. Could you come to my birthday party on Thursday?
xíng wǒ yí dìng  lái
行, 我 一 定  来。
Sure.
Dialogue Two
hēi lǐ méi  zhè me qiǎo
嘿,李 梅, 这 么  巧!
Hi, Li Mei. What a coincidence.
hēi dà chuān shì a zhēn qiǎo zhè  zhōu  sì néng  lái
嘿, 大  川。 是 啊!真  巧! 这  周  四  能  来
cān  jiā wǒ de  shēng  ri  jù huì ma
参  加 我  的  生  日 聚 会  吗?
Hi, Dachuan. Yes, this is a coincidence. Could you come to my birthday party on Thursday?
èn  wǒ zhōu sì wǎn shang yǒu kè bù  néng  qù le
嗯…… 我  周  四 晚   上   有  课,不  能  去 了。
hái shì yào  zhù nǐ  shēng  ri kuài lè
还  是  要  祝  你  生  日 快  乐!
Oh I'm sorry, I'm busy! I have class this Thursday evening. Still, I wish you a happy birthday!
méi guān  xi  xiè xie
没  关  系。谢  谢!
No problem. Thanks!

Explanation of difficult points

1. 为什么
"为什么" (wèi shén me) means "why". "为什么" is usually put at the beginning of a sentence. The sentence which begins with "为什么" can be ended with a question mark, it can also be ended with "呢" (ne)+ "?" or "呀" (ya) + "?".

2. 这周四(你)能来参加……
In "这周四(你omitted)能来参加……" [zhè zhōu sì (nǐ) néng lái cān jiā], the subject "你" (nǐ) is omitted because it is assumed. "来" (lái) can also be omitted, but it is added for emphasis to mean "participate" as opposed to simply "coming to participate". It is commonly said in everyday spoken Chinese.