The words 'much' and 'many' is used before nouns. The word 'very' is used before adjectives. The difference between 'much' and 'many' is that 'many' is used for countable things and 'much' is for uncountable.

Roman has given you an excellent answer. I'll just add a few examples: 1. Much + uncountable noun How much money do you need? There isn't much time. 2. Many + countable noun How many people are there in your family? There are many ways to learn a language. 3. Very + adjective/ adverb This hotel is very expensive. The train is going very slowly.