I was looking through the Learn > Chess Basics section and none of the subsections are working on the mobile site. I have tried using both Safari and Chrome on mobile (iOS) and whenever you click on one of the Chess Basics sections (e.g., Combat), the screen loads and then freezes and you can't start the game.

And I try to teach chess to my kids :)

I've never used lichess in mobile, but you can try using the app.
I recommend using a desktop/laptop for lichess.

Yeah i now the App, but the Sites lichess.org/learn#/ are not available in the app. It is just the blue "starting" overlay that doesn't work on any mobile. I think its an easy fix: just get rid of it ;D