Proxmox on Hetzner, 2 IPs - 1 NIC - no subnet, routed configuration

i need help with my PROXMOX / VM network problems :S that problem is similiarto but only similiar: Proxmox Routed Network Configuration on Hetzner Server

i got no inet connection with my VM debian/11, Hetzner gaves me 2 IP's:

49.12.XXX.31/26 first one: D4:5D:XX:BC:E9:9B 49.12.XXX.25/26 second one mac: 00:50:XX:00:19:A3

both got the same gateway and brcst 49.12.XXX.1 49.12.XXX.69

here is my server/proxmox config:

source /etc/network/interfaces.d/*

# Loopback device:
auto lo
iface lo inet loopback

# device: enx12905253282a (second networkadapter gbic = not in use)
iface enx12905253282a inet manual

# device: enp195s0
auto enp195s0
iface enp195s0 inet static
    address 49.12.XXX.31
    netmask 255.255.255.255
#   hwaddress D4:5D:XX:BC:E9:9B   ###i tested twice with hw and without
    pointopoint 49.12.XXX.1
    gateway 49.12.XXX.1
    up sysctl -p

iface enp195s0 inet6 static
    address 2a01:4f8:XXX:5b6c::2
    netmask 128
    gateway fe80::1
    up sysctl -p

# einzelIP
auto vmbr0
iface vmbr0 inet static
    address 49.12.XXX.31
    netmask 255.255.255.255
#   hwaddress 00:50:XX:00:19:A3     ###i tested twice with hw and without
    bridge_ports none
    bridge_stp off
    bridge_fd 0
    bridge-disable-mac-learning 1
    up ip route add 49.12.XXX.25/32 dev vmbr0

iface vmbr0 inet6 static
    address 2a01:4f8:XXX:5b6c::3
    netmask 64
    up ip -6 route add 2a01:4f8:XXX:5b6c::/64 dev vmbr0

i followed the guide from Hetzner 120%, the german once.

VM cfg:

source /etc/network/interfaces.d/*

auto lo
iface lo inet loopback

auto ens18
iface ens18 inet static
  address 49.12.XXX.25
  netmask 255.255.255.255
  pointopoint 49.12.XXX.31
  gateway 49.12.XXX.31
  dns-nameserver 1.1.1.1
  hwadress 00:50:XX:00:19:a3

iface ens18 inet6 static
  address 2a01:4f8:XXX:5b6c::4
  netmask 64
  gateway 2a01:4f8:XXX:5b6c::3
  hwadress 00:50:XX:00:19:a3

i can ping from VM to 49.12.XXX.31 and from PROXMOX to VM 49.12.XXX.25

my sysctl:

net.ipv4.ip_forward = 1
net.ipv4.conf.enp195s0.proxy_arp = 1
#net.ipv4.conf.all.rp_filter=1
#net.ipv4.conf.default.rp_filter=1
#net.ipv4.icmp_echo_ignore_broadcasts=1

net.ipv6.conf.all.forwarding = 1
net.ipv6.conf.all.accept_ra = 2
net.ipv6.conf.all.accept_redirects = 1
net.ipv6.conf.all.accept_source_route = 1
net.ipv6.conf.default.disable_ipv6 = 0
net.ipv6.conf.all.disable_ipv6 = 0

maybe a little spelling mistake ? I would be grateful for help!!

chris