Back-office → Localization → Translations. On the loaded page select “Installed module translations” and “YOUR THEME” than click to your language (flag). Find “YOUR_MODULE” and translate this module to your language. If you didn't find the searched text, try to look for it in the default theme (Default theme-Installed module translations-YOUR LANGUAGE).
Here is the video of this process:
The default prestashop title pages you can translate here:
Back-office > Preferences > SEO & URLs
and here > Preferences > CMS Categories