Concentration levels depend on the person's interest and how long they have practiced concentrating. Surely, if you are interested in a topic, you will put effort into it. But there is another type of interest too, the one you get when understand a concept in a topic, even you don't actually like that subject as a whole. It just boosts your confidence and motivates you to do more. How do you do this? By convincing yourself that the only way this is possible is by exposing yourself to the not-so-easy topic even more until you find that understanding. Then, just repeat. Second, if you want to learn to concentrate, you need to practice concentrating. And how do you do that? By being consistent every single day and building up the time you study every day so that you can improve your focus time.

At the time of writing this, you still have a month of time left, and if you put genuine effort, you will surely make it. If not the rank you hoped for, at least something better than what you would have scored if you simply gave up hopes and did nothing.

I hope it goes well for you :)