We've all been there - 50+ circuits on that still doing the same thing... Still feeling behind the aircraft, until one day it just clicks. Everything falls into place, you stop worrying as much and start relaxing (a little - not too much). Then it is finally time for your first solo.
There is nothing wrong with feeling as though you still need to keep learning, many thousand plus hour pilots keep reminding me that they still learn on most flights! I know that I definitely still learn so much on every flight, perfect my skills (or lack thereof) until I can get proficient at it! It isn't easy, but this applies to both theoretical and practical knowledge.
All that I will suggest, is not drinking alcohol and getting as much sleep as you can on the two nights before every training flights (at least giving yourself 8+ hours to sleep on both nights prior to the lesson). You will see a major improvement on your ability to learn, and to act according to your wishes. Generally the rest alone will be a massive help, but you'll feel more rested, and relaxed if you don't drink alcohol. Those things completely overhauled my entire learning schedule, and allowed me to progress from circuits to solo, and form solo to navigation. Had I not realised this, it would have taken me considerably longer to pass.
As your theoretical knowledge seems to be escaping you, why not use your app (or where-ever you have questions - each chapter of the book?) to keep practicing the different chapters every evening before bed? It will re-enforce your knowledge base. Plan routes on your charts, use your flight computer to make calculations with current weather etc.. All good practice!
But then again... Just don't rush it, enjoy it! Your initial flight training is as valuable if not more-so than anything else you might potentially face later on - so make the most of it!
good luck with your training!