DNS changes do not happen immediately. The changes need to propagate to other servers. It is entirely possible that your systems administrator has made changes that are not visible to other DNS servers yet.
primary name server = ns1103.ui-dns.org
responsible mail addr = hostmaster.1und1.com
serial = 2017060103
refresh = 28800 (8 hours)
retry = 7200 (2 hours)
expire = 604800 (7 days)
default TTL = 600 (10 mins)
Your zone refresh is set to 8 hours. I've checked all of the major DNS providers and nobody has your A record except your ionos host.
Just give it some time. I checked their servers and they just added both your A and AAAA records.