Can i import user data into an form and auto fill the form with this information (adress, name etc.) if the user enters the form with a prepared unique link?
There isn't any method of importing data. We did just add a new feature that might help your use case: "Save Web Form", this can be enabled and configured on the "Options" tab and allows users to partially fill out the form and then save it to complete at a later time, this provides a URL that will be populated with the data the user had filled out. You, as the form author could always fill in the required user data for the specific user, save and then send them that custom URL.
The URL times out after a set period (up to 28 days) and is invalid once it has been submitted or saved again (saving again at a different point creates a new URL).
Hopefully this helps for your workflow.