I know im far too late, but some advice in case anyone else ever comes across this thread whilst searching for help;
Don't change the render thread settings in any of the c4d preferences, nothing you change here will speed up rendering. The only reason to change these settings is to lower the thread count to leave some cpu power reserved for other tasks. Otherwise you will only make things worse.
Same for the memory settings. Those settings change how much memory the ram player can use, increasing this memory will *decrease* the memory available for rendering. So again, just dont change them, reset them back to defaults.
As for how to speed up the scene; the best thing for that scene is to reduce the reflection depth. You have soft blurry metal and soft blurry paint, these each reflect off each other. In the render options, reduce reflection depth down from 5 to 1 or 2. the lower it goes, the faster it renders, though it will also get slightly darker.