Change entity with business process flow

Hi everyone,

I just tried to create a business process flow, which changes the entity from opportunity to a custom entity.

like this:

https://technet.microsoft.com/de-de/library/dn887193.aspx

But when i am doing this only the fields of the business process flow "change" the entity.

The form still ist the form of the opportunity, but i want it to change to the form of the custom entity.

How can I enable that feature?

Best regards

Daniel