Widening the webpage.

Hello, I’m still a WP newbie and I need some help with my site at:
https://www.juliesinteriordesigns.com/

I’m looking to remove the dotted vertical lines between the menu items at the top.

I’m also looking to widen the slider panel with the pictures in the middle of the site as well as the space that my slider and text reside in. This is the square in the middle of the page with the dotted lines around the border of it. I need it to be wider to fit more items.

Thank you in advance for the help.