We are looking for a developer with good coding skills and knowledge of Spanish to integrate the Xiaomi Treadmill into Home Assistant

Compensation is for fun and in your spare time for the benefit of the Home Assistant community. The Strava path seem not to be the easiest way for us personally:

https://petergamma.org/instructions-which-are-available-to-integrate-strava-to-home-assistant/

It might be better to connect it to the Balena Health Balena Home Assistant fusion:

Or simply make a Home Assistant Integration for the Xiaomi Treadmill. Code for it can be found be google for it. We then have a treadmill on which we can track our heart rate in Home Assistant.