Hello,
Please try to add this code in Theme Options > Custom css > Custom css for desktop:
.blog .sidebar,
.single-post .sidebar {
position: sticky;
top: 0;
right: 0;
}
.blog .fixNav-enabled .fixed-already + .container + .header-wrapper + .page-heading + .container .sidebar,
.single-post .fixNav-enabled .fixed-already + .container + .header-wrapper + .page-heading + .container .sidebar {
top: 150px;
}
Regards