This website provides missing tutorials for the Qt framework and C++ of intermediate difficulty. Feel free to explore.
“Raise your quality standards as high as you can live with, avoid wasting your time on routine problems, and always try to work as closely as possible at the boundary of your abilities. Do this, because it is the only way of discovering how that boundary should be moved forward.” ― Edsger W. Dijkstra
Watch Matt P. Dziubinski's video from CppCon 2016 on Computer Architecture, C++, and High Performance.