I downloaded your File. I “”fixed it” to be in the right format. I changed the EDM field name to one I have. It imported perfectly.
The issues you are having I believe has to do with your csv file. You had a backslash / in front of the url…that will not import correctly as it will be read special character, you had a / in front of your registration
you do not need sl_registration, just the word registration, also you normally would not usea hyphen in a slug but separate rather with an underscore. I do not know if that matters. But I have attached the cleaned up version that I imported into my site with the extended data field slug I have added, i.e test