Mpu9255 cant get z axis data

Using Arduino Programming Questions
1

I have that MPU9255: https://himalayansolution.com/product/mpu-92-65-gyroscope-and-accelerometer-module-3-axis
I want to angle of yaw movement and here is my code:

#include <SoftwareWire.h>

SoftwareWire wire(2,3);

const int SENSOR_ADDRESS = 0x68;

void setup() {
  // put your setup code here, to run once:
  wire.begin();
  Serial.begin(115200);
  wire.beginTransmission(SENSOR_ADDRESS);
  wire.write(0x6B);
  wire.write(0x00);
  wire.endTransmission(true);
  delay(50);
  wire.beginTransmission(SENSOR_ADDRESS);
  wire.write(0x1C);
  wire.write(0x00);
  wire.endTransmission(true);
}

void loop() {
  // put your main code here, to run repeatedly:
  wire.beginTransmission(SENSOR_ADDRESS);
  wire.write(0x3B);
  wire.endTransmission(false);
  wire.requestFrom(SENSOR_ADDRESS, 6, true);
  int16_t xAxisFull = (wire.read() << 8 | wire.read());
  int16_t yAxisFull = (wire.read() << 8 | wire.read());
  int16_t zAxisFull = (wire.read() << 8 | wire.read());
  float xAxisFinal = (float)xAxisFull / 16384.0;
  float yAxisFinal = (float)yAxisFull / 16384.0;
  float zAxisFinal = (float)zAxisFull / 16384.0;
  Serial.print("x Axis = ");
  Serial.println(xAxisFinal);
  Serial.print("Y Axis = ");
  Serial.println(yAxisFinal);
  Serial.print("Z Axis = ");
  Serial.println(zAxisFinal);
  Serial.println("-------------");
  delay(500);
}

and here is my output:

x Axis = 0.00

Y Axis = 0.02

Z Axis = 0.93

There is no problem to get roll and pitch angles but when sensor make yaw movement there is no change in z axis value.
And that is the output when sensor make roll movement:

x Axis = 1.00

Y Axis = 0.02

Z Axis = -0.13

z axis value is decreasing same amount as increase amount of x axis value. And this is the pitch movement output:

x Axis = 0.05

Y Axis = 0.99

Z Axis = -0.14

Same as roll movement.
How can I get angle of yaw movement.

2

The magnetometer can be used as a compass, to measure yaw.

The accelerometer can measure only pitch and roll, as described here: How_to_Use_a_Three-Axis_Accelerometer_for_Tilt_Sensing-DFRobot

3

Accelerometer is 3 axis:
Forward/backward
Left/Right
Up/down

Edit: Gyro should do:
Pitch
Roll
Yaw

You can make a single axis gyro with 2 accelerometers using a differential output.
Six accelerometers would do all 3 gyro axes. I could boil that down to 5.