Hi Alessandro,

First, we usually use the word noun (rather than substantive) for what you would call "substantivo" in Portuguese.

For "count nouns" (things that you can count like apples, coins or years) we use many.

For "non-count nouns" (things that you cannot count like sugar, water or ignorance) we use much.

Examples:

How many cookies did you eat?

How much sugar did you buy?

There is a different italki section for questions.  You will get more help if you post in the questions section.

English Grammar in Use 4th edition by Raymond Murphy is excellent. The paper copy is reasonably priced and there is a PDF on the net.

Unit 69

excerpt

We use many and few with plural countable nouns.

We use much and little with uncountable nouns.