First you speak about "Sequence, Selection, Repetition, Object-Oriented (Encapsulation, Inheritance, Polymorphism)" (that are general programming concept not necessarily specific to C++) then you talk of GUI in term of Win32 and MFC.
Well ... how much you want to study and how much you need to be immediately productive? How much "business" and how much "reaserch" is behind your "production"?
If you did GUI with Java and VB and you know C++ you will have no problem with C# or C++/CLI.
If you want to understand the how the OS work, go to Win32 or XWindow(for Unix/Linux), no chance. But that's plain C.
If you need a C++ representation of a GUI, MFC is one of them. But it's not "Up-to-date" C++ programming, and is Windows only.
If you need to be multiplatform, then start with something simple, like FLTK
] (The last C++ book from Stroustroup has samples with it), than consider GTKMM
If you want better "modern C++ programming" library, consider VCF
] or Algierlib
](still in development.