I'm a little confused with what you said so please bear with me.
From the sound of what you said in your post - re: web interface, it sounds like you might have a WordPress.com account or a WordPress website hosted somewhere similar to how WordPress.com works.
What is your website address?
Are you on WordPress.com by any chance?
This support forum where you are posting at is for self-hosted (meaning, the WordPress websites are hosted on a server that people who are requesting support have access to... for example, I own WordPress websites on my own server space) WordPress sites.
That aside, it generally is possible to back up the CONTENTS of your WordPress website regardless of where it is hosted.
If you look in your Admin panel and click on the Tools, there is an Export link. If you click that, it will open a page that gives options for backing up your site's contents.
This file can be imported into a new WordPress website (or other website using a content management system compatible with WordPress data importing).
It is NOT meant to serve as a full and complete backup, but it will help you to collect and export your website content into an importable file.