Quantifiers

I think "much" is used in questions and in negative statements before uncountable nouns, such as, "I don't have much time" or "He didn't have much to say."



Yes. Of course, the meaning changes.



No, that's very awkward, even though it's understandable. See my above statement about "much."

I hope that's helpful.

Fine.But why I can't say: "Can I lend you much money?" It's a question, using "much" is awkward here...Why??????

Because languages aren't terribly logical. We don't choose words as individual, interchangeable units, like parts of a machine. Rather, we choose language items in clumps called collocations, idioms, set phrases, etc, based on our exposure to conventional usages, logical or not. So, at home I might learn to use "ain't no," but at school they'll tell me not to.

Instead of trying to analyze any language using logic, it's far better to simply learn the conventions. I recommend googling Krashen's Second Language Acquisition Theory. It's not flawless, but it explains a lot.