Raspberry-Pi to APM :: Drone Control Connection Help (Hyderabad ONLY)

I need expert help troubleshooting my wired connection (USB/Serial) between my APM flight controller and Raspberry Pi, as I'm experiencing connection issues. I'm attempting to control my drone this way, but I'm running into problems.

Ideal Skills:
- Experience with APM flight controllers
- Proficient in Raspberry Pi troubleshooting
- Knowledge of USB/Serial connections
- Drone programming and control experience

I need someone that is local to Hyderabad, India. Its easier for me to brainstorm.