Confusingly, this module is a combo of two chips, and one of which is a combo of two chips. 

The module is commonly referred to a the GY-91, which is a MPU-9250 (9 axis g/a/m sensor) chip, plus a BMP280 (absolute barometric pressure sensor) chip.

The MPU9250 is two dies in one package; from the Product Specs: 

MPU-9250 is a multi-chip module (MCM) consisting of two dies integrated into a single QFN package. One die houses the 3-Axis gyroscope and the 3-Axis accelerometer. The other die houses the AK8963 3-Axis magnetometer from Asahi Kasei Microdevices Corporation. Hence, the MPU-9250 is a 9-axis MotionTracking device that combines a 3-axis gyroscope, 3-axis accelerometer, 3-axis magnetometer and a Digital Motion Processor™ (DMP)

https://www.invensense.com/wp-content/uploads/2015/02/PS-MPU-9250A-01-v1.1.pdf

I had Google a library before a fully grasped the above, and so tried to use this lib which is not the correct one.   https://github.com/kriswiner/ESP32/tree/master/MPU9250_MS5637

Yeah, don't try that.