Get network access from my virtual machine with qemu and Debian Host

I have a (hopefully) simple problem.

I try to configure my host system to route network traffic through one physical network interface.

Here is my setup:

I have an ethernet interface (eth0) and i have a bridge already running. Important to this setup is. I had to switch the Mac-Adress because the hoster seems to only allow traffic on the main Mac-Address. So.

This is my interfaces config for br0 and eth0:

auto br0 eth0

iface eth0 inet manual
    hwaddress ether 9e:91:af:f2:79:ef

iface eth0 inet6 manual
    hwaddress ether 9e:91:af:f2:79:ef

iface br0 inet static
    address 89.58.62.11/22
    gateway 89.58.60.1
    hwaddress ether 0a:a2:e9:ed:76:99
    bridge_ports eth0
    bridge_stp off
    bridge_maxwait 0
    bridge_fd 0

iface br0 inet6 static
    address 2a0a:4cc0:1:242::1
    gateway fe80::1
    hwaddress ether 0a:a2:e9:ed:76:99
    bridge_ports eth0
    bridge_stp off
    bridge_maxwait 0
    bridge_fd 0

As you can see i configure br0 to use ipv4 and ipv6 and eth0 (the physical interface) is just added to the bridge br0.

Now i want an VM with a second physical IPv4 (official IPv4) and hopefully an IPv6 from my net.

I run the guest in an qemu instance with these starting conditions (currently):

#!/bin/sh
qemu-system-x86_64 -machine type=pc-q35-2.12,accel=tcg -smp 6 -m size=4G,slots=2,maxmem=12G -k de -device virtio-net-pci,netdev=net0 -netdev tap,id=net0,"helper=/usr/lib/qemu/qemu-bridge-helper" -device qemu-xhci -spice port=5900,password=mysecretpw -vga qxl -drive file=hda.img,if=virtio,bus=0,unit=0,media=disk,cache=writeback -drive file=/opt/cdimages/debian-11.5.0-amd64-netinst.iso,media=cdrom,index=0 -drive file=/opt/cdimages/virtio-drivers.iso,media=cdrom,index=1

Additional: My routing table on the host

Kernel-IP-Routentabelle
Ziel            Router          Genmask         Flags Metric Ref    Use Iface
0.0.0.0         89.58.60.1      0.0.0.0         UG    0      0        0 br0
89.58.60.0      0.0.0.0         255.255.252.0   U     0      0        0 br0

And now its up to you. Can anyone help me to get my guest running with my second official IP:

89.58.20.44/32

Oh. Btw. My Host-System is a Debian 11 Server.

If it is important: The host system is a "root"-server which means it is also a vm with physical attached hardware. But i have access to everything on the host like a dedicated server.

I hope someone can help me.

Greetings

Christian Nill