A private, inaccessible, IANA/IETF-reserved IP address was found for bbb.mahale-ggmbh.de. Let's Encrypt will always fail HTTP validation for any domain that is pointing to an address that is not routable on the internet. You should either remove this address and replace it with a public one or use the DNS validation method instead.
fe80::4cd3:54ff:fee3:105c
A and AAAA records found for this domain
bbb.mahale-ggmbh.de. 0 IN A 45.146.254.209
bbb.mahale-ggmbh.de. 0 IN AAAA fe80::4cd3:54ff:fee3:105c
An internal error occurred while checking the domain
Failed to query certwatch database to check rate limits: pq: canceling statement due to conflict with recovery