Hi Jerry,
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Anyway, I find VFP a great tool, and don't want to leave it, just think I must add some more to my toolbox as you said. Would you please help me a bit more? What do you think should it be my right choice at the moment: C++ or C#? What I want? Better understanding of the behind the scenes action, the ability to build wrapped win API function calls (to easy VFP usage), my own functions (those that could not be done easily in VFP) etc. I don't mean (if that's not necessary) to build apps in C++/C# of course!

Not an easy question. It depends alot on you and your likes and dislikes, and the business climate in the region where you work.

C# is a tool Microsoft devised that would be Java-like, after Sun stopped MS from embracing and extending Java itself, and is presently restricted to the WinXX platform. It seems destined, as I sense it, to be part of .NET and the "pay-per-use" HailStorm stuff. You may want to consider cross platform Java tools like Sun's Forte, or IBM's Visual Age for Java 3.0. I've run VAJ 3.0 on both WinXX and Linux and it runs IDENTICALLY on both platforms, and the source code is 100% interchangeable. Both of those tools have been available for free on the Linux Platform (recommend SuSE 7.2 Pro or Mandrake 8.0, around $50 US.) and would allow you to learn without costing you a bundle of cash. The KDE Linux Desktop also includes KDevelop, a VERY powerful C++ GUI-RAD IDE, including version control and built in docs for C++, the QT toolkit, and KDevelop itself, which is GPL and FREE. And Glade, too, which is another GUI-RAD IDE that uses the gtk+ toolkit and C. Glade is not as well developed as KDevelop. Then, of course, there is always Kylix! ;-)