There is not much difference between C and C++. C++ is a super-set of C and derived from it; the language basics are the same (and hence C/C++) but C++ added the object oriented 'stuff'. Variable types, control structures, functions, it's all the same in C and C++.
If you really want to learn C/C++, learn it on a PC (as Robin indicated). It teaches you how to properly construct a program. No Arduino Builder that takes a little bit of work out of your hands but sometimes drops a stitch and you have no idea what is wrong.
If you use Linux (and the same probably applies to the Mac), it comes with C and C++ compilers. For Windows, you can download a free edition of Visual Studio; it used to be called Express, I think it's now 'Community Edition'); just check if it supports C++, I think it does. There are plenty other free compilers available for Windows.
Next when you start using Arduino, you have a solid foundation but there are minor differences. There ain't things as reading keyboard and writing to screen (as the Arduino does not have them). And there are a few libraries added so you can read pins and control outputs and the likes.
One of the reasons why I started using Arduino was that I had never done C++; C yes, C# yes, several scripting languages and assembly yes, but never C++. Also I still don't use the OOP part much, I do have a better understanding of C++ than I had before.