Yeah, that's the strange thing. I can see orders and order items in the database but not in the frontend although I can see products both in the database, in the shop and in the frontend.

That means there must be something wrong with the data rows in the database. But there is not much I changed. I just set the auto increment parameter. Perhaps I should not have done that. I will export the data schema from shop A again and import it without removing anything. After that I will remove items step by step.