https://addons.mozilla.org/de/firefox/addon/deutsch-de-language-pack/versions/

"Hmm. We’re having trouble finding that site. We can’t connect to the server at addons.mozilla.org."

is it offline ?

https://addons.mozilla.org is loading fine.

On https://addons.mozilla.org/firefox/addon/deutsch-de-language-pack/versions/ it lists the versions of Firefox each one is for as many of the recent ones are listed for Firefox 143.0 to 143.* which is on Beta channel currently as Fx 143.0 is not scheduled for release until September 16. The second one down Version 142.0.20250827.4350 states it works with Firefox 142.0 to 142.*

Note the Language Packs are for changing the language of the User Interface like the menus and such as the spell checker uses dictionaries that is on right side of https://addons.mozilla.org/firefox/language-tools/. Just mentioning this as I have seen many people asked questions on why they could not add languages for the spell checker over the years.

site is down :-(

Please check your network connect and DNS settings,it's work seccssful?