Found the reason! My clutch was ok and
Peter from Ebike Motor Center recommended me to check one of gears inside the gearbox. They are pressed together, but there is no spline on the gear, also only about 2/3 inside of the gear touches the spline. The inner side got stripped and now it can...
100% its not a speed sensor... This error appears, cause motor starts to assist, but has no connection with cranks. The wheel rotates slowly, while the motor gives all its boost. Thats why when u pedal with motor off - sensor works fine. I suppose the clutch bearring suddenly died...