Take a look at these
open-source-erps[
^]
ERPNext seems to be the most interesting one as it uses Python and JavaScript.
As I never used one of these and am not a Pyton programmer, I can not tell if it is a good idea to use Python for something like this.
If speed is a major concern another language like Go would probably be a better choice, see:
Best-programming-language-to-learn-for-backend-developers[
^]