Oil level OK
Added after 3 [hours]: The case was finally resolved ... according to the suggestions of Carrot and Kwok, the indicator in accordance with the operating manual, which I found on the Internet, means the oil level is too low (or if the level is ok, the sensor is damaged - as in my case).
I am enclosing a photo of the instructions - sorry for the low quality.

I would like to thank the Forum members for their help!