How to move Page content more into center/how to get sidebar visible on posts

Hi there

I have two issues I am currently working on and I think they are probably pretty simple but I am still new to this

1) When I go to the blog posts entry area, the right hand side bar has dissapeared entirely (it’s a secondary sidebar/sidebar a) (not sure if I need to change that in a PHP file for the posts or if its changeable in CSS? and what exactly I should place there to get it to pop up again (as it does in the pages)

an example of the blog https://www.talipurkerson.com/category/blog/
an example of a page (about me template) https://www.talipurkerson.com/contact

2) The main content in the center (on pages- like the content page above) is still over to the left- is there a way I can get it more centered and remove the space between the main page content and the right sidebar?

Thanks so much in advance to responders!