You don’t have much time.
I have a lot of questions.
You don’t have a lot of time.
When we speak about countable things, we use many. For example cars, trees, books and apples.
When we speak about uncountable things, we use much. For example money, time, space and air.
We can use a lot of for countable and uncountable things.
I have many goats.
I don’t need much money.
I have a lot of parrots.
I have a lot of time.
You can see more examples in the book Robinson Crusoe.