Hi,
I'm a Chinese Malaysian, I can understand basic chinese for communication
I've done development of IMU sensors on STM32f3 Discovery Kit using Madgwick's filter to get quaternion numbers and Euler angles.
My recent work on underwater robot, we use MPU9250 as feedbacks, it is much more easier to use as the library is provided
I have the relevant experience and I need to understand more about your problem.
Drop me a message.
Best regards