Edit custom fields using free edition when you can't add any more custom fields

Edit custom fields using free edition when you can't add any more custom fields

I need to edit the field type but I reached the max fields but I do not need all those fields but I need some. I would like to delete the ones I do not need but do not know how or if it is possible. I could change the field type but I need to create a new field type but can't because I reached the limit. So the first step would be to permanently delete the custom fields I do not need but is that possible I can only see a way to move them out of the lay out but not a way to delete them.