Following are one of the best and most authentic sources to learn from:
If you are an Indian and are unable to understand English lectures properly then Saurabh Shukla is the best teacher you can find online and that too for free over Youtube, you can refer to this Link
If you want to learn the basics and the overall syntax of the language and want to get started super fast then Bucky from newboston channel on YouTube has created really great playlist of C++ basics, it is one of the best resource to kickstart you journey in C++, you can get it here.
Udemy also has some of the great instructors of C++ you can check Abdul Bari’s course with nominal price and it also offers certificate of completion, you can get it here.
If you enjoy reading articles and can absorb them better than the videos, then, GeeksForGeeks is the best website for any kind of help regarding C++. You can go through the exhaustive list here and can read them as you like. link
If you want to go for some of the fancy courses on C++ then you can try Coding Ninjas, Coding blocks, and many other similar websites but I don’t recommend you these websites as some of them are very costly and you won’t get satisfaction after the completion, in my opinion these courses are not worth of the amount they are charging.
You can also try freecodecamp C++ tutorial which covers all the basics and is available in single long video, so you don’t need to navigate through different playlists and videos as everything is presented at a single place. Here is it’s link
Other good course on C++ is on educative website, it provide a really good user experience and covers the topics in detail, you can check the course here: Learn C++ from Scratch - Learn Interactively
Edx also offers great courses developed by tech giants like Microsoft, Amazon, etc. and the good thing is they also provide you certificate which can act as testimonial of your efforts( you can argue that nowdays certificates have no value and all what matters is skill, you are right but what’s wrong in having them as byproduct of your learning, at least, they are better from nothing :) ). It also has courses by really great universities throughout the world. Here is the course link of Microsoft’s self paced course: Introduction to C++
You can learn from any of the above mentioned websites. But at the end everything boils down to how much you practice, how deeply have you understood the concepts. There are loads and loads of other resources as well but the above mentioned ones are by far the best I’ve seen till now.
Now, practicing is as important as learning a new concept. For practicing you can go to HackerRank, http://hackerrank.com/domains/cpp , and can practice any topic related to C++ by selecting subdomain and difficulty levels, within few weeks you’ll notice a great change in your language proficiency.
Hope it helps!!
Wishing you a great learning ahead :)