How should I learn all the cases?

First of all, you do not need to learn every case as there are just too many to learn. Second, there are different cases for the same points so just remember the one that is easier for you (though make sure it is correct and valid, of course). Case and reference learning is probably the most tedious part of Law and I find the best way to learn cases is to just drill them routinely, even if it's just 5 minutes a day which increases as you approach the exam. You'll be thankful for those daily 5 minutes in exam term. Try using apps like Quizlet which uses flashcards and memory tests, also making sure you have a basic understanding of the topic involved is vital. Personally, I always remembered cases of areas of law I found really interesting so if there is an area you're struggling to remember I recommend reading some articles or case notes around that. If you have a genuine interest and personal viewpoint in that particular area then the cases will come a lot easier. Other techniques I used included making stories or connections based on the name, such as imagining a giant can of soup outside of a post office in Campbell.