'Many' and 'much' are both used to indicate a large quantity . 'Many' is used with countable nouns ( people, animals, flowers etc) and 'much' is used with uncountable nouns (Water, sugar, salt etc) Although 'much' is used more in the negative and 'a lot of' is used more in the positive.'There is a lot of water in the well.' 'There isn't much water in the well.'
Both are used with the question word 'how' to ask about quantity. How many brothers do you have? 'How much sugar do you take?
Both are use with 'of' to indicate a portion of something. 'Much of the food is fresh' 'Many of my friends are students.
Both are used with 'so' to emphasize quantity. 'So much chicken is left over from last night.' 'So many chips are bad for you.'
Both are used with 'more' to make comparisons. 'I have much more money than you.' 'He has many more friends than she does.'
Both are used with 'too' to say the quantity of something is more than necessay or good. 'Too much wine is bad for you.' Too many chocolates will make you fat.'
'Much is also used as an adverb to say to a greater degree or extent. 'much smarter' .
And much can also be used as a noun. 'Much has been said about the problem, but little done.'