The space between RIGHT sidebar and RIGHT INNER sidebar

It’s hard to tell just from looking at an image. Can you post a link to your site? Have you tried changing the value for RIGHT INNER sidebar WIDTH in the options?

https://stixopad.ru/

Go to Appearance > Atahualpa Theme Options > Sidebars & Widgets > Style & configure SIDEBARS and change RIGHT INNER sidebar WIDTH from 180 to something like 120.