If your training is carried out how it should be, nothing should stand in the way of successfully completing your interim and final exams.
The final exam assesses whether you have the necessary skills and knowledge that are required by your chosen career. In order to sit the final exam, you must have successfully passed the interim exam.
It is also possible that your final exam is split up into two different parts, with the first part of the final exam being more like an interim exam. In this case, you should contact your union for advice. You must submit your complete, signed report book in order to sit the final exam. If these requirements are not met, you will not be permitted to sit the exam.
As a trainee under the age of 18, you are allowed the working day before your written exam free (§10 of the JArbSchG).
If you know from school that you are liable to suffer from exam-related stress, a seminar held by your youth union could help. You can find up-to-date seminars and dates on their websites.