removind the widgets from the sidebar areas under ‘dashboard – apperance – widgets’ does often not work, as the theme uses hardcoded replacement codes instead for the sidebar.
you might need to go through all theme templates, and remove the code <?php get_sidebar(); ?>; and then adapt the CSS to stretch the content section over the full width.
consider to create a child theme for the customization.
for details, please post in your theme support section at https://www.ads-software.com/support/theme/portfolio-press
PS:
a crude ‘CSS only fix’ could start with adding this via a ‘custom CSS’ plugin:
#sidebar { display: none; }
#content { width: 100%; }
