This is how I would suggest that you attack this assignment:
1) Figure out what points you want to make. Since this is a character sketch, you want to focus on Mr. Nuttel's character traits. What words or phrases describe Mr. Nuttel's behavior?
2) Once you have your list of traits (I would recommend at least 3-5), look back in the story for examples of Mr. Nuttel behaving in this way. For example, if you say Mr. Nuttel was shy, what does he do in the story to support that he is shy.
3) Write a paragraph for each trait, using your support to flesh out your paragraphs.
4) Your topic sentence should include all of your traits and should be somewhere in your introduction. For example, "Mr Nuttel was a nervous, shy person who lacked confidence and was easily fooled by Vera because of his gullibility."
Now, you are ready to write your essay! Put it all together and good luck!