In case you have trouble with the main domain name linux-forks.de of the server you can try the backup name lag-land.de .
If that does not really help, you can use one of these names:
|ipv4.lag-land.de||force the use of the IPv4 address|
|ipv6.lag-land.de||force the use of the IPv6 address|
|18.104.22.168||raw IPv4 address|
|2a03:4000:35:2c0::1||raw IPv6 address|
When only the raw IP address works for you then you have probably a problem with your DNS resolver, but that is in most cases in the hands of your ISP.