Hi,
Go to the page's Properties -> URLs tab. There you can change the Page alias property - which is then used also in the menu web parts. You can also use the custom page URL path or define also page aliases.
If you are using the "Use name path for URL path" setting (https://docs.kentico.com/display/K9/Settings+-+URLs+and+SEO), you can then change just the page name on the Form tab in the field that is set as the page name source.