[Answer]-Issues with storing data in groups

This, to begin with, will help you understand the error you’re getting

group_id = Group.objects.get(id=1)

Here, group_id becomes an instance of the model Group.
Group and its instances have attributes name, and permissions.

group_id.groups.add(new_user)

Is nonsense. groups is an attribute of User and not Group.
Replace group_id with new_user :

new_user.groups.add(group_id)

This will add group_id (which should be named group instead) to the list of groups new_user is member of.