Automated headings within Atticus (like automated chapter numbers) currently only appear in English. You can manually change the title and subtitle of any chapter/page in Atticus, but if you select Chapter Numbers to appear in the header, this text will be in English.
Option 1: Deselect Number under Visible Chapter Details on the formatting page.
Option 2: Select the numeral only style under Chapter Number View
You can rename your Table of Contents page on the Writing Tab by clicking on your TOC in the left navigation pane. This will open the TOC in the editor pane, where you can add a custom title at the top of the page.