Hi @marcelolz
For a field to appear. it must exist in either the database or the functions.php file.
Have you got any PHP registered fields in your functions.php file?
Also, why did you delete the fields?
There is a guide here which will explain what happens when you update from v3 to v4
http://www.advancedcustomfields.com/resources/getting-started/migrating-from-v3-to-v4/
