Problem with the rover speed with the topic trajectory_setpoint

Hello, after many tests on the rover, I realized that the velocity following y therefore msg.velocity[1] gives a combination of speed following x and yawspeed. Besides, the msg.yawspeed doesn’t work by adding it to a speed along x. The rover doesn’t turn.

I wanted to know if this was normal since it seems quite weird anyway. Are there parameters to modify to manage only the yawspeed and the longitudinal speed without touching the msg.velocity[1] ?