"Please pay the money back immediately" 意思是 "请立刻还钱"。

这句话的来源是英语的基本语法和词汇，"please" 是礼貌用语，意思是 "请"；"pay" 是动词，意思是 "付钱"；"the money" 是名词短语，意思是 "钱"；"back" 是副词，意思是 "回来"；"immediately" 是副词，意思是 "立刻"。

下面是一些英文例句及其中文翻译：

Please pay the money back as soon as possible. 请尽快还钱。
Can you please pay the money back by tomorrow? 你能明天还钱吗？
I need you to pay the money back now. 我需要你现在就还钱。
It's important that you pay the money back on time. 你按时还钱很重要。