Installation on a fritzbox 7430 not worked

Hi,
I have a problem with installation of openwrt.
If I see the file "openwrt-lantiq-xrx200-avm_fritz7430-squashfs-sysupgrade.bin" in the /tmp directory of the rooter I have to start the sysupgrade with the command: sysupgrade -n /tmp/openwr...bin.
after this I get this:
...upgrade: Commencing upgrade. Closing all shell sessions.
Command failed: Connection failed
root@OpenWrt:/#
After this the rooter boots with the AVM-os.

This are the running processes:

root@OpenWrt:~# ps
  PID USER       VSZ STAT COMMAND
    1 root      1928 S    /sbin/procd
    2 root         0 SW   [kthreadd]
    3 root         0 IW<  [rcu_gp]
    4 root         0 IW<  [rcu_par_gp]
    5 root         0 IW<  [slub_flushwq]
    6 root         0 IW<  [netns]
    8 root         0 IW<  [kworker/0:0H-ev]
   10 root         0 IW<  [mm_percpu_wq]
   11 root         0 SW   [rcu_tasks_trace]
   12 root         0 SW   [ksoftirqd/0]
   13 root         0 IW   [rcu_sched]
   14 root         0 SW   [migration/0]
   15 root         0 SW   [cpuhp/0]
   16 root         0 SW   [cpuhp/1]
   17 root         0 SW   [migration/1]
   18 root         0 SW   [ksoftirqd/1]
   20 root         0 IW<  [kworker/1:0H-ev]
   21 root         0 IW<  [inet_frag_wq]
   22 root         0 IW   [kworker/0:1-eve]
   23 root         0 SW   [oom_reaper]
   24 root         0 IW<  [writeback]
   25 root         0 SW   [kcompactd0]
   30 root         0 IW<  [pencrypt_serial]
   31 root         0 IW<  [pdecrypt_serial]
   43 root         0 IW<  [kblockd]
   44 root         0 IW<  [blkcg_punt_bio]
   45 root         0 SW   [watchdogd]
   48 root         0 SW   [kswapd0]
   49 root         0 IW<  [kworker/0:1H]
   50 root         0 IW   [kworker/u4:2-ev]
   60 root         0 IW<  [kthrotld]
   76 root         0 IW   [kworker/u4:3-ev]
  201 root         0 IW<  [mld]
  202 root         0 IW   [kworker/0:3-eve]
  203 root         0 IW<  [ipv6_addrconf]
  204 root         0 IW<  [dsa_ordered]
  214 root         0 IW   [kworker/1:2-mm_]
  215 root         0 IW   [kworker/1:3-eve]
  259 root         0 SW   [ubi_bgt0d]
  438 ubus      1480 S    /sbin/ubusd
  439 root      1052 S    /sbin/askfirst /usr/libexec/login.sh
  474 root      1196 S    /sbin/urngd
  609 root         0 IW<  [kworker/1:1H]
  891 logd      1476 S    /sbin/logd -S 64
 1101 root      1264 S    /usr/sbin/dropbear -F -P /var/run/dropbear.1.pid -p 22 -K 300 -T 3
 1217 root      2064 S    /sbin/netifd
 1333 root      1736 S    /usr/sbin/odhcpd
 1746 root      1948 S    /sbin/vdsl_cpe_control -i10_00_10_00_00_04_00_07 -n /sbin/dsl_notify.sh -f /tmp/lantiq-vrx200-b.bin -l /tmp/lowlevel
 1812 root      2904 S    {ntpd} /sbin/ujail -t 5 -n ntpd -U ntp -G ntp -C /etc/capabilities/ntpd.json -c -u -r /bin/ubus -r /usr/bin/env -r /
 1814 ntp       1368 S    /usr/sbin/ntpd -n -N -S /usr/sbin/ntpd-hotplug -p 0.openwrt.pool.ntp.org -p 1.openwrt.pool.ntp.org -p 2.openwrt.pool
 1842 root         0 SW   [autbtex]
 1843 root         0 SW   [pmex_ne]
 1844 root         0 SW   [pmex_fe]
 1999 root      2904 S    {dnsmasq} /sbin/ujail -t 5 -n dnsmasq -u -l -r /bin/ubus -r /etc/TZ -r /etc/dnsmasq.conf -r /etc/ethers -r /etc/grou
 2007 dnsmasq   1708 S    /usr/sbin/dnsmasq -C /var/etc/dnsmasq.conf.cfg01411c -k -x /var/run/dnsmasq/dnsmasq.cfg01411c.pid
 2247 root      1284 R    /usr/sbin/dropbear -F -P /var/run/dropbear.1.pid -p 22 -K 300 -T 3 -2 9
 2248 root      1372 S    -ash
 2330 root      1376 R    ps
root@OpenWrt:~#

Does anyone have any idea how I need to prepare the sysupgrade?

Thanks for help.

Did you do the part starting with "Before flashing"?

I do not understand what you mean.
I first started the router with openWRT. But openWRT was only in RAM. The original OS (from AVM) is in FLASH. Then I copied the installation file of openWRT to the /tmp directory. When I wanted to start the FLASH process, I got the error message described above.