SOLVED. Fantasy book about stone split in 4? [s]

[Henriette]

It is more than 1 part and starts with a boy given to a young prince to be punished for the bad things done by prince.
They become friends later. The stone split in ? parts is given to dwarfs and elfes. Please help me find the books because I read them maybe 20 years ago but when I bought my ereader I gave all my paper books away.
And I want to read the story again.

[Anna]

Well of Darkness

[Henriette]

Yes! I had to search for the Dutch version to really recognize it but it's the book I was looking for!
Thank you very much!