Are you talking messy on the page in the admin or messy on the front end of a site.
You cannot change the field names in ACF, doing so will loose any data that was saved. Also the field keys must be the same.
You can’t “duplicate” a field group, this changes the field keys and duplicates the field names. Field names must be unique.
The way to move fields from one group to another is to create an empty field group and save it and then edit the original group and use the “move” option for each field to move it to the new group.
