Hello,
I have no idea how to translate the front page of my website
Check the 4th point:
1) Activate Polylang
2) Create your languages => Settings > Languages > Tab Languages
3) Choose your permalinks => Settings > Permalinks
4) Create your static front pages (if necessary) per language
=> Pages > Add new
4.1) Define your static front page => Settings > Reading
5) Choose your Polylang settings => Settings > Languages > tab "Settings"
6) Create your widget => Appearance > Widgets
7) Create your content which go in menus
8) Create your menus => Appearance > Menus. Put in your menus at least one page (homepage ..) or post if you want they appear on your website.