Many and much are the words we know as adjectives but one often gets confused with their usage.

Many is used as adjective before a countable noun
many errors, many trees, many people, many leaves…

Much is used as adjective before an uncountable noun
much worries, much coffee, much stress, much joy...

However, both these words have the same comparative and superlative forms i.e more and most.
more trees, more coffee…
most leaves, most damage…