"If you really want to learn C++, I advise against any and all online tutorials and against most books. Without any kind of quality control, many professional book writers published many awful C++ textbooks that may be easy to read and sell well, but teach lies. Stick with the community-verified book list available at StackOverflow"
In other words, use the StackOverflow list to choose the right teaching material [2]. A Tour of C++ (Bjarne Stroustrup) has been a good refresher, with C++ Primer (Stanley Lippman, Josée Lajoie, and Barbara E. Moo) as the primary reference for further clarification. Also use GeeksForGeeks and LeetCode practice problems.
[1] https://www.quora.com/Which-is-the-best-book-for-learning-c+... [2] https://stackoverflow.com/questions/388242/the-definitive-c-...
I figure you didn't mean to call it out specifically and more meant general smart pointers, but just felt I'd let you know that searching for that terminology may lead you astray.
Not only that -- it was removed in C++17!
I wouldn't get too hung up on skipping straight to "modern" C++. Yes, C++11 is a game changer, but the vast majority of what you'll find in the classic recommendations is still worth knowing. Things like type deduction, smart pointers, and move semantics won't be hard to pick up once you've got the basics. Although I haven't read it, Accelerated C++ sounds like a good fit for your situation.