Thank you for purchasing our theme and for reaching us.
Please try to change options in Theme Options > Blog & Portfolio > Blog Layout.
Available image size settings you may find in Settings > Media. Don’t forget Regenerate thumbnails https://wordpress.org/plugins/regenerate-thumbnails/
Also, you may try to edit lifestyle/framework/templates/index.php and lifestyle/framework/templates/content.php files. We recommend to make changes in a child theme to prevent of losing modifications after theme update.
