the lan side network interface appears to be completely gone, so it doesn't matter what you put there, it still won't work.
tried a reset ... ?
if you manage to set the static wan side IP, as you need from the ISP, you could wget the openwrt file over internet.... OR put another router, that works with the ISP, between the SamKnows and your ISP.
He is on the bridge.
who is ? the captain ?
How to put in static IP inside /etc/config/network ?
config interface 'wan'
option ifname 'eth0'
option proto 'static'
option ipaddr 'a.b.c.d'
option netmask 'v.x.y.z'
option gateway 'k.l.m.n'
don't forget to restart the network afterwards.
it wasn't the expected result.
wget the image directly over internet, via serial console.
Yes, it is. However, the current firmware is not the official OpenWrt and it almost certainly operates very differently since it is highly customized by the vendor.
You are not only missing the lan side network, but also the firewall and DHCP configuration files.
Either something is very wrong with that installation/configuration, or the vendor has done something very very different than normal.
I'd recommend resetting the device to defaults. You may be able to do this with the standard openwrt method:
firstboot -y && reboot
If that works, it will hopefully get the normal networking functioning properly so that you can upgrade to an official modern version of OpenWrt.
If you cannot get it to reset, you may need to ask the vendor how to reset it or how to get the normal networking to function.
How do I put a static ip to use WinSCP?
Currently, you can't. Something is wrong with the device -- it will not work properly, and to fix it, you need to follow my advice from earlier:
What was the outcome of the wget?
You've been asked three times already, to perform a reset, why haven't you?
I already did the reboot, I need to edit /etc/config/network, so that I have a static ip to be able to connect to WinSCP.
The router already comes from the factory with a bridge.
config interface 'loopback'
option ifname 'lo'
option proto 'static'
option ipaddr '127.0.0.1'
option netmask '255.0.0.0'
config interface 'wan'
option ifname 'eth0'
option proto 'dhcp'
config interface 'wan6'
option ifname 'eth0'
option proto 'dhcpv6'
config interface 'wlan2g'
option proto 'dhcp'
option metric '1'
config interface 'wlan2g_6'
option proto 'dhcpv6'
config interface 'wlan5g'
option proto 'dhcp'
option metric '2'
config interface 'wlan5g_6'
option proto 'dhcpv6'
config switch
option name 'switch0'
option reset '1'
option enable_vlan '0'
config switch_vlan
option device 'switch0'
option vlan '0'
option ports '0 1 2 3 4 6'
Weg does not work.
reboot or reset? Did you follow this advice:
Previously your post showed that the dhcp and firewall files did not exist... if you reset properly, they should hopefully be there (unless there is something unique about how SamKnows built their firmware).
Please copy the output of the following commands and post it here using the "Preformatted text </> " button:
Remember to redact passwords, MAC addresses and any public IP addresses you may have:
cat /etc/config/wireless
cat /etc/config/dhcp
cat /etc/config/firewall
Did you reset your device with the commands I provided?
Yes, the router comes from the factory bridged, so I have to add a fixed ip, but I don't know.. 
Please show us what happens when you run the commands -- show us the output from the screen.
option ifname 'lo'
option proto 'static'
option ipaddr '127.0.0.1'
option netmask '255.0.0.0'
config interface 'wan'
option ifname 'eth0'
option proto 'dhcp'
config interface 'wan6'
option ifname 'eth0'
option proto 'dhcpv6'
config interface 'wlan2g'
option proto 'dhcp'
option metric '1'
config interface 'wlan2g_6'
option proto 'dhcpv6'
config interface 'wlan5g'
option proto 'dhcp'
option metric '2'
config interface 'wlan5g_6'
option proto 'dhcpv6'
config switch
option name 'switch0'
option reset '1'
option enable_vlan '0'
config switch_vlan
option device 'switch0'
option vlan '0'
option ports '0 1 2 3 4 6'
that's not what I asked for... please show us the output of this:
What are you doing? The last time that user posted was over 2 years ago... tagging people into your thread in this way is frowned upon.