It is really impossible for me to say because it so much depends on how much time you have available in the 3 weeks (are you able to study all of the time, or are you working?) and also how hard or difficult you find the topics.
If you are able to spend whole days studying then do give it a go and hopefully you will make it OK. (But do watch our free lectures – our notes are only lecture notes and are meant to be used while watching the lectures. They are not a Study Text to be used on their own.)