It is important to learn all of the subjects well, and as you recognise the way things are run in Europe tends instead to encourage question spotting. If you've passed the written exams, firstly well done, secondly what new might you learn?
The first thing you can do is go back to the texts you learned from, and re-read those. Find a good library and read further into the most interesting topics such as meteorology, aircraft technology, aircraft performance.
Anderson's "Introduction to Flight", or Davies "Handling the Big Jets" are books you'll learn huge amounts from, if you'd like recommendations.
Frankly, reading ICAO annexes is for the aviation lawyers, don't waste your time.
And spend a lot of quality time on the manuals of aircraft you'll be flying - you can't know too much about an aircraft you fly, and that will do you a lot of favours.
G