now I have to take the written exams again
No, you will never have to take the written exams again.
May it be that after a certain amount of time I have to start from 0 and pay another 10k for flight training etc?
No, not that either, you have to go to an approved school (ATO) and do as much training as they recommend to pass a Proficiency Check. If your Class 2 medical privileges have expired, you will need to obtain at least a Class 2 as well.