I don’t know much about how to speed it up, but maybe this will help.
You could cancel rebuilding in the process because first, it adds .cpp and .h files and then starts to rebuild. You could disable compiling when adding a new C++ class by going Edit → Editor preferences → Miscellaneous → Hot reload → Automatically compile newly added C++ classes.
Upgrading hardware will improve or you could try out Incredibuild. It accelerates compilation time in Unreal Engine and it doesn’t require any setup, just install it on your machine and Unreal Engine will use it automatically. Hope it helps 