I mean only my servers have static addresses (dns server, dhcp server, web server, one machine for routing,...).
The servers have their DNS pointed to the DNS server which i have configured manually.
No that was actually the main issue.
I just realised i haven't properly installed everything to make it work and that it's beyond my knowledge for the moment. Apparently i have to use rncd.key, configure the named.conf and options, which i didn't do cause i don't know how.
I didn't even know what nsupdate was or a TSIG error... Welp, i'm gonna study some more and try again.... Thx anyway.