Is it possible to remove left and right white space around the top page/post image?

The white space is part of the design, but if you want to remove that, you can use this custom CSS as a workaround.

.post-image {
    margin-left: 0;
}
.blog-list .post-content-container {
    width: 32.5%;
}
.single-post .post-image,
.page .post-image {
    margin: auto;
    width: 100%;
}
.single-post .post-image img,
.page .post-image img {
    display: block;
    margin: auto;
}
.content-width,
.page-template-template-featured-works .theme-widget-area.content-width {
    width: 1105px;
}
.page-template-template-featured-works .content-width {
    width: 77.66%;
}
@media only screen and (max-width: 1600px) {
    
    .page-template-template-featured-works .content-width,
    .theme-widget-area.content-width,
    #content-container {
        width: 1105px;
    }
}
@media only screen and (max-width: 1165px) {
    
    .page-template-template-featured-works .content-width,
    #content-container,
    .content-width {
        width: 100%;
    }
    .theme-widget-area.content-width {
        width: 90%;
    }
}
@media only screen and (max-width: 950px) {
    .blog-list .post-image {
        width: 100%;
    }
    .blog-list .post-content-container {
        width: 58%;
    }
}
@media only screen and (max-width: 768px) {
    .blog-list .post-content-container {
        width: 70%;
    }
}
@media only screen and (max-width: 600px) {
    .blog-list .post-content-container {
        width: 90%;
    }
}