...
Please take a close look at RealFlow | Cinema 4D's list of limitations and known bugs. It is a valuable resource when you encounter problems, crashes, or difficulties:
System requirements
Cinema 4D R15, R16, R17, Cinema4D R18, R19, R20, R21, S22, R23, S24 and R25 (64 bit only)
Windows 7 (or higher) or macOS 10.9 (or higher) operating system.
CPU 64-bit Intel® or AMD® multi-core processor.
8 GB RAM.
100 MB disk space for installation.
Network adapter and internet access for license activation.
RealFlow | Cinema 4D supports GPU-based simulations and multi-core/multi-processor systems.
...