@rino19ny snow rider said in whats the correct way?:

is there some kind of learning map on how to proceed learning to use Qt for c++ coding and GUI development?

like being able to move old dBase III systems to Windows or Plasma including the "windows" developed?

C++ Basics: Ensure you have a solid understanding of C++ fundamentals, including classes, inheritance, polymorphism, templates, and the Standard Template Library (STL).
C++ in Qt: Focus on how C++ integrates with Qt’s meta-object system, signals and slots mechanism, and Qt's unique data structures.
Sample Learning Path
Week 1-2: Install Qt and learn basic Qt widgets.
Week 3-4: Dive into advanced widgets, signal-slot mechanisms, and custom widgets.
Week 5-6: Study Qt Quick and QML for modern UI development.
Week 7-8: Explore database integration with Qt.
Week 9-10: Begin migrating and modernizing your dBase III system.
Ongoing: Continue to refine your skills, explore advanced topics, and stay updated with Qt’s latest features.