Join the small Meeting C++ mentoring group which meets twice a week to speak about the current things that matter to you in C++. As part of this group Meeting C++ will offer some limited 1:1 mentoring slots where you'll be able to focus in a 2 hour session each week to improve your C++ skills. This gives you a place to ask your questions and learn the important details of modern C++. A mentoring group runs for 2-3 weeks a month.
Meeting C++ has a wide web of C++ knowledge build through the last decade. This includes conference talks, blogs and lots of personal contacts in the C++ community.
You should fit into a junior group which wants to explore modern C++ and maybe Qt. Qt will sometimes be a good example on how to interact with code that applies idioms and patterns differently. That is written in a different style and embraces OOP more then modern C++ does. But your needs and questions will guide the learning experience in the group.
I favor a small group, so access to the mentoring program is fairly limited. This is not a program where you learn by your self in an online course.
As a C++ programmer I have many years of experience in important libraries such as Qt, boost and the standard library. I've also worked with dlib, wxWidgets, OpenCV and other libraries. For many years I have worked as a freelancer in C++, seeing lots of code bases and different styles. Organizing Meeting C++ since 2012 has given me insights in modern C++ and its development in the last decade. I'm know C++11 - C++17 well, and have started applying C++20 where it fits.
My part in the program is to answer your questions, and see what additional resources could be helpful. Over time this will build a knowledge base which is available to you.