Wrong import or bad model?

When I import my .obj file to Substance Painter, then whole UW map goes on the side, so, I can`t paint anything

Don't use Ctrl+V to paste an image directly into a message. Use the "My Files" button, upload the picture to the site and add a link to the message (this is a reliable method, the picture will be stored on our server).

Or save the picture in any storage and provide a link to it (this is not a very reliable method; the picture may be deleted from a third-party service).

Or the picture must be very small in order to immediately paste it using Ctrl+V.