Good day, i am a beginner. How can I indicate the road, that on one side of the motor traffic is banned. Edits in potlatch. Thanks for the answer.

What do you mean by “on one side motor traffic is banned”?
If you mean motor traffic is only allowed in one direction, then tag it as a oneway street.
If you mean it is two separate carriageways, with some sort of divider in the middle, then draw it as two separate ways. In Potlatch you can select the way, then choose the “Restrictions” tab, then set whether motor vehicles are allowed.