Solved requirenments for building Cinema 4D extension

what knowledge should to learn for writing Cinema 4D plugin, for example; c++, OpenGL ,,, ?

Cinema4D can accommodate plug-ins written in C++ or Python. However, it only accept scripts written in Python.

Hi angel23, thanks for reaching out us.

With regard to your question the answer can be pretty wide depending on the depth you're aiming to tackle.

Cinema 4D comes as @bentraje properly stated with C++ and Python APIs: whilst the first is bigger and more comprehensive the second is a specialized subset of the first and easier to approach.

For the Cinema 4D API newcomers we recommend to stick to the Python API which gets rid of all the hurdles of the building process and to get proficient with it.
Upon getting used to it and to the foundation Cinema 4D API concepts, moving to C++ won't be too complex.

Best, Riccardo