Think like this: How many: you can count how many there is e.g. How many people are coming? How much: if you can't count how much there is e.g. How much is this fruit?

You use 'many' for individual items, and 'much' for quantities. Or - in other words, you use 'many' for countable nouns, and 'much' for uncountable nouns. So - 'many apples', 'many people' - 'much concrete', 'much luck', 'much wine'.

"many" for countable "much" for uncountable