Learn advance versions of C++ (i.e. C++11/14/17) as they covers the gaps & issues we normally face in old C++. Not only this will help you to understand why & how these issues occurred & what measures were taken to prevent them, but it will also make you familiarize with other languages too. Since, at that point of time, not only C++ was getting updated with these new features but also the other languages in a bit different format, but the concepts behind them were similar. Like JavaScript, whose constructs are pretty comlpex, but a person with C++ background will have less difficulty to understand them.

Furthermore, you will be introduced with the concept of Functional Programming, which becomes very helpful in learning other concepts such as Concurrent/Parallel Programming. Moreover, C++11 have introduced Move-Semantics (a.k.a rule of five) which heavily optimizes your code.

So, here is a great article for starters which will give you brief intro about the major differences in advance versions:
C++11 vs C++14 vs C++17