If I know C++ very well, will I eventually learn the "real" C language (without any "differences")
If you learn C++ properly, you will probably not need to use many of the standard techniques used in C. Theoretically you could program almost anything C in C++, with exceptions that have already been introduced. However, in reality, you wouldn't - or shouldn't. This is because C++ is a different language that provides a very different set of tools when used optimally.
Aside from the very basic elements like general syntax and fundamental types, these are two separately evolving languages, and they should be approached (learned, programmed) as such.
