There is already a VB script for Linux and Windows in GitHub: https://github.com/johnboiles/hotspot_autologin
It works by grabbing session token (json) from: https://hotspot.vodafone.de/api/v4/session And send to: https://hotspot.vodafone.de/api/v4/login
But this method is not that convenient for mobile device. I didn't find a great way to read json in an automation app.