Thanks Maxim for your help. But then where to write this proxy_pass:

proxy_pass http://www_serveriai_80;

And still, going further in my site, https drops off and i'm being left only with http. How to permanently stay on https, but in this location:

location /SomeService {
proxy_method POST;
proxy_pass http://10.255.6.120:8080/SomeService;
proxy_set_header Host $http_host;

to stay always on http.
Thanks

Regards,
Karolis