Dear Client,
We are an english speaking python/javascript developer and have been working with erpnext for quite some time, We can show you our development servers and apps we have develop under de frappe framework (Erpnext Framework) and the internal mods we have done to erpnext itself, since erpnext its the software we use for billing, human resources and other task.
We would like to discuss the extends of your project and even If you agree schedule a demo of the functionality you want.
Best regards and lots of success
Jesus