Plugin hides orders when deactivated

As we integrated another Payment system that gives us all the methods we need, I wanted to deinstall the Plugin, and as I deactivated it, The orders that I had, were not listed anymore.

There is also another problem with it, that affects also other orders not just the one that was created with the payment Kauf auf Rechnung.

It set both orders , the oone that was already payed with Paypal also to Mahnung. That is not OK at all.

Now I need your help to deconnect the order from your Plugin, to be able to delete your plugin without hiding my orders.

The page I need help with: [log in to see the link]