Sidebar in Twenty Nineteen

We need to see your site with both these sidebars to help

Here is URL : https://project.cybermarketingservice.com/

Can I import Bootstrap in sass folder ? I have seen another theme having bootstrap folder inside the folder of sass

Looks like you went with the bootstrap approach

Yes, but there is a problem. When I make changes in styles.css of child theme they are override by bootstrap. Can you suggest solution for this ?