Sidebar width

Hello,
In my WP blog (https://money-socrates.com/online/ ) I am using the “Online Marketer” theme. Everything was perfectly OK until now when I made some changes on the pages titles in the Menus. Since then, the sidebar dissapeared from all pages including the Home page. I have checked the pages attributes and all of them use the “Default Template” (exactly as before when the sidebar was perfectly shown), and not the “Full-width, no sidebar”.
When I go to any page, the sidebar appears momentarily and dissapears immediately.

Also, 2 or 3 days ago I tried to change the sidebar width from (I think) 300 to 100. I do not remember how i did that, maybe through style.css or else? However the sidebar width did not change at all until today.

I would appreciate your help to resolve this problem. Thank you.