You didn’t provide a link to your site, but try this.
If you’ve a created a child theme, then copy the rules below into your child theme’s style.css file. Otherwise, use a CSS plugin like Jetpack or Custom CSS Manager. Don’t modify the theme’s style.css file directly. Any changes made to a theme file will be wiped out the next time you update/upgrade the theme.
.home #sidebar {
display: none;
}
@media screen and (min-width: 59.6875em) {
.home .site-content {
margin-left: 0;
}
body.home:before {
display: none;
}
.home .site-content {
width: 100%;
}
}
body:before {
background-color: rgba(255, 255, 255, 0.4);
}
This will remove the sidebar from the home page.
As far as making the sidebar transparent on other pages, I assume it is because you added a background image and you want it to show through. The last rule should do that. In this line:
background-color: rgba(255, 255, 255, 0.4);
The last parameter for the rgba function, 0.4, is the opacity level. The valid values are from 0 (completely transparent) to 1.0 (completely opaque). so a value of 0.4 means 40% opaque (60% transparent). You probably don’t want it completely transparent, unless your background image is light enough to where your users can view the sidebar text. But adjust it to your liking.