Apex domains cannot have CNAME records.
Question and response
Question
dig germany-1.vps.ac. NS
Answer
germany-1.vps.ac. 5 NS ns2.fotbo.host.
germany-1.vps.ac. 5 NS ns3.fotbo.cloud.
germany-1.vps.ac. 5 NS ns4.fotbo.org.
germany-1.vps.ac. 5 NS ns1.fotbo.com.
Authority
The response has no authority records.
Additional
ns1.fotbo.com. 4 A 161.35.148.32
ns2.fotbo.host. 4 A 45.77.141.178
ns3.fotbo.cloud. 4 A 95.216.169.27
ns4.fotbo.org. 4 A 5.161.207.181
ns1.fotbo.com. 4 AAAA 2a03:b0c0:2:d0:0:0:289:b001
ns2.fotbo.host. 4 AAAA 2001:19f0:6c01:2178:5400:4ff:fe7e:f2fb
ns3.fotbo.cloud. 4 AAAA 2a01:4f9:c012:4e7f:0:0:0:1
ns4.fotbo.org. 4 AAAA 2a01:4ff:f0:bd58:0:0:0:1
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0