Question

We appreciate your giving us so much of your precious time!i

Answer 1

首先 giving在这里不是进行时,进行时是be doing形式,在这里 giving 是动名词,就是动词的名词形式,因为在your（物主代词）后面,必须用动名词.

其次,这里用了was,确实是过去时,原因是 “giving us so much of your precious time”（给我们这么多美好时光）是过去发生的事情,所以用了was,是说,在那个时候,It was our pleasure.