zuó tiān wǎn shàng wǒ děng nǐ dào shí diǎn
Xiao Li: 昨天晚上我等你到10点。
Last night, I waited for you until 10 pm.
duì bú qǐ wǒ bú shì gù yì fàng nǐ gē zǐ de
Lulu: 对不起,我不是故意放你鸽子的。
Sorry, I didn't mean to stand you up.
tài bú kào pǔ le wǒ yào hé nǐ jué jiāo
Xiao Li: 太不靠谱了,我要和你绝交!
You are totally unreliable. Our relations end here!
dé le bié xiǎo tí dà zuò le
Lulu: 得了,别小题大做了。
Come on, it is not a big deal.
In the dialogue, Xiao Li is furious with his friend Lulu for being kept waiting for such a long time the previous night. Lulu apologizes and says she didn’t mean to "放鸽子(fàng gē zǐ)", which literally means "fly a pigeon". This phrase is used when someone is a no-show for a meeting, much like the term ‘being stood up’ in English. We can say,"我被放鸽子了" (I’ve been stood up), or "她放我鸽子了" (She stood me up).
"靠谱(kào pǔ)" is an adjective to describe a person or a thing. If you trust a person, you can say,"他是个靠谱的人" (He is a reliable person). If you think a task can be finished with a very high success rate, you can say "这个方案非常靠谱" (This plan is very reliable). In the dialogue the opposite word "不靠谱" is used to describe a person as being unreliable because they did not show up for a pre-arranged meeting.
The idiom "小题大做" (Literal meaning of each character: small-problem-big-do) is basically the same as the English idiom "making a mountain out of a molehill". The idiom is used to describe when someone overreacts to a trifling problem.