You are studying irregular verbs to speak and write correctly in the past time. You have learnt a lot after having read Treasure Island but you need practise and ,of course, great interest on your side. Remember that you have to learn those verbs by heart. Here you have a video to watch, read and listen to a list of verbs. This will help you. After that you can practise by speaking and writing those verbs on your own too. Visit the post on our wiki to learn more.