Answer:
15) We had a lot of fun at Wiliam's party.
16) How much water did he drink? I think he drank a lot.
17) There isn't much time left and I have many things to do.
18) There are many things to choose from. I don't like having many chocies.
19) Have you got much oranges left? I thought you had many of them.
20) There are many things you can do to improve your English, but there isn't much you can do if you don't make an effort.
(Hope this helps) Sky