Question

帮忙分析一下这个句子的句子结构

standing beside the counter was a customer who overheard the conversation between the two

Answer 1

a customer who overheard the conversation between the two was standing beside the counter.
这个句子是个倒装句，是为了避免头重脚轻的，属于修辞的需要。
还原为原句后如上。

主语是a customer， who overheard the conversation between the two是定语从句，修饰主语， 而后面的was standing beside the counter.是个系表结构。

可以这样翻译，一位顾客，当时正站在柜台旁，无意间听到了两人之间的对话。

Answer 2

and well 这个整个做为一个主语,因为这个句子本身省略了同样的词以避免重复.如果不省略那就是:
Learning to read rapidly and (Learning to read )well,也就是说and 在这里做连词,连接两个副词状语.这里我们可以翻译为:
学会快速有效的阅读...

整个句子翻译为:
学会快速有效的阅读 (presupposes)也就预示着(that you have the necessary vocabulary and comprehension skills )你要有足够的词汇量和一定的理解能力.

问题补充,如果well是修饰 presupposes,那么就应该把and去掉,变成:
Learning to read rapidly well presupposes that you have the necessary vocabulary and comprehension skills.
翻译为:学习快速阅读很好的预示了.....(整个句子的意思不一样了)

不然语法错误了. 正因为and是连词,并列前后两个成分.前面的的Learning to read rapidly是短语,后面的怎么可以是句子呢?而且是缺少主语的.