Reverse proxy if target server does redirect

Hi all,
I want to have Nginx as reverse proxy into my smart home.
E.g. the location home shall reverse proxy my Homematic system:

location /home/ {
proxy_pass http://192.168.23.120/;
}

What the target (which I reach nicely) does is forward to /pages/index.htm?<sessionID>

Nginx converts that to http://my_nginx_server/pages/index.htm?<sessionID> -> where I get a 404 (which is correct ;-) )

-->how do I have to setup Nginx that it creates http://my_nginx_server/home/pages/index.htm?<sessionID>
-->how can I tell Nginx to proxy a whole substructure of a target server?

Thanks in advance,
Ben