At any time, you can rollback your actions and set the "demo data" again to start learning again. In this case, most of your settings will be deleted and the site will return to its original state. Do not use this already on a finished site, as you will lose data. Go to " Modules -> Design Management " and click install demo data.
PS The same manipulations must be performed when changing the template (all settings and the product base will be lost. Therefore, the template is selected only 1 time during installation).