Change Sidebar width and styling correct

1. hello How can i change sidebar width? I need to change sidebar width himself and not content there. i need to decrease him from 100% to 50%.

2. On Pages under the logo and up to breakcurbs i see turquiese small square. how can i remove them? my URL Is: https://msdi-ltd.com (not http://www.msdi-ltd.com !)

3. are it possibe to make separator betwen sidebar and content? if yes so how? maybe is css costom code

Thanks