When you add a new page to your website, its URL automatically mimics the page title. If you rename the page, the URL is also automatically updated. Non-Latin symbols are replaced with Latin symbols:

However, if you duplicate a page, or if the alphabet you use is not recognized, a random page ID is generated and attached to the URL:

It's very simple to fix it! Open the Pages and navigation panel on the left and then open the settings of a particular page:

Edit the page URL and save the changes: