つもりです=intend to I intend to go to the moon one day. :D と思います=think I think he may do it. にします=take I'll take a rain chack. おう=chase The guy being chased by caps If you give me some examples of にします and おう, then I may give you a better answer.

わたしはそれをするつもりです。= I am going to do it, or I plan to do it, or I intend to do it, depends on context. わたしはそれをすると思います。= I think I will do it. わたしはそれをすることにします。= I have decided to do it. わたしはそれをします。= I will do it. わたしはそれをしたいです。I want to do it. I didn't get 動詞おう　means. If it was どうしよう。then it means "What should I do?"