Debian 11 bullseye How do I manage the IPV6 interface? And can I reload the resolv.conf file?

My config : Raspberry - Raspbian - Debian 11 Bullseye - CM4 Package resolvconf My

/etc/network/interfaces

auto eth0
iface eth0 inet static
address 192.168.100.125/24
gateway 192.168.100.100
dns-search test.local
dns-nameservers 192.168.100.101 192.168.100.102
iface eth0 inet6 static
address 2001:0db8:3c4d:0015:0000:d234::3eee:0000
gateway 2001:0db8:3c4d:0015:0000:d234::3eee:0100
dns-nameservers 2001:0db8:3c4d:0015:0000:d234::3eee:0101 2001:0db8:3c4d:0015:0000:d234::3eee:0102

I modify

/etc/network/interfaces

with shell script using sed command, I restart my network with

sudo systemctl restart networking

**My first problem**: When I put dhcp to static, my dns configuration isn't updated on resolvconf, so I have the new static dns and the last dhcp dns. Same thing when I put new ipv6 DNS and when I delete it I keep the last ipv6 DNS configuration after rebooting the network. I do not know if I can refresh resolvconf file to keep only dns configuration by

/etc/network/interfaces

. **My second problem**: When i set my ipv6 static all works fine, i can change them, but when i want passed with dhcpv6 or autoconfiguration i cannot restart my network, i have this error.

sudo systemctl status networking.service
● networking.service - Raise network interfaces
     Loaded: loaded (/lib/systemd/system/networking.service; enabled; vendor preset: enabled)
     Active: failed (Result: exit-code) since Wed 2021-11-24 09:14:57 CET; 6min ago
       Docs: man:interfaces(5)
    Process: 856 ExecStart=/sbin/ifup -a --read-environment (code=exited, status=1/FAILURE)
   Main PID: 856 (code=exited, status=1/FAILURE)
        CPU: 151ms

nov. 24 09:14:57 debian dhclient: than a configuration issue please read the section on submitting
nov. 24 09:14:57 debian dhclient: bugs on either our web page at www.isc.org or in the README file
nov. 24 09:14:57 debian dhclient: before submitting a bug.  These pages explain the proper
nov. 24 09:14:57 debian dhclient: process and the information we find helpful for debugging.
nov. 24 09:14:57 debian dhclient:
nov. 24 09:14:57 debian dhclient: exiting.
nov. 24 09:14:57 debian ifup: ifup: failed to bring up eth0
nov. 24 09:14:57 debian systemd: networking.service: Main process exited, code=exited, status=1/FAILURE
nov. 24 09:14:57 debian systemd: networking.service: Failed with result 'exit-code'.
nov. 24 09:14:57 debian systemd: Failed to start Raise network interfaces.

I looked for advice for this problem but everything I could find about a configuration file at the address

/etc/network/interfaces.d/setup

that I don’t have. So I don’t know where this problem can come from. Have you ever encountered any of these problems? If you have any leads I am a taker. I can’t give you additional configuration because I don’t have the raspberry on the weekend.