For the PPL exams:
It depends where you're doing your PPL exams, as they differ from country to country. In the UK, I'd recommend the "EASA PPL Exam" app, as they contain many questions similar to the ones in the real exams. But as it looks like you're in Italy, the best preparation will most likely be to read the books carefully and ask your instructor for specific advice.
For the Flying Test - as Tobster says, just relax. I found that by having several flights with different instructors towards the end of your training helped a lot with regards to relaxation.
Good luck!
Alex