For #3, Django documentation helpfully describes a method. 3)
https://docs.djangoproject.com/en/2.2/topics/i18n/translation/#how-django-discovers-language-preference Not sure of sample project, but a simple Google serach on for a GitHub page is enough
For #2, Built-In admin is still possible in production. When deploying, you need to make sure that in your URLConf, you change the path from admin/ to something really strange like iuh494vnun2ijnuhj-2ejv02ijv4-/ so that users don't know that you're using Django and so they can't guess whatever your superuser password is.
For #1, Django is supposed to be an easy web framework. I'm not sure if there's an open-source project anywhere else that is alike your idea since most are totally unique from each other. I'd suggest that you simply get on Django and try it out.
The issue with Django is mostly the deployment part. It's wildly not fun, there aren't that many tutorials (or at least those that are good), and there can be a lot of difficulties with them. I mean, there is "python manage.py check --deploy", but the true deployment is difficult, and there is no GitHub project that makes it simple.
All in all, views aren't that difficult to understand. Learn a bit of models and views and the Django way of template building, and you'll get the hang of it real quick. Additionally, with templates, it's simple HTML. You can download a website builder, like Google's, and copy-paste the code to a Django application.
Good luck and don't sweat it.