I don't know how to use "much" and "much more" to modify adjectives? For example, I know it's much cheaper, but I want to know, why can't I use much more soap?

I don't know how to use "much" and "much more" to modify adjectives? For example, I know it's much cheaper, but I want to know, why can't I use much more soap?

First of all, you should know that the comparative degree of adjectives and adverbs can be divided into monosyllabic and polysyllabic