Nginx proxy_pass is not passing customized header into the server

I have Nginx installed on my machine and serve 2 domains.

1. https://example.com/ -> Frontend.
2. https://api.example.com/ -> Backend.

I'm communicating backend application through the frontend, But it's seem to be that the backend application does not receive any header from the Nginx.

This is my Nginx.conf:

user  nginx;
worker_processes  auto;

error_log  /var/log/nginx/error.log;

events {} # event context needs to be defined to consider config valid
http{
    include /etc/nginx/mime.types;
    server {
        listen 80;
        root /usr/share/nginx/html;
        server_name studenttracker.co.il;

        location / {
            try_files $uri $uri/ /index.html;
        }

    }
    server {
        listen 80;
        server_name api.studenttracker.co.il;

        location / {
            proxy_pass_request_headers      on;
            proxy_pass http://159.223.2.114:8443;       
            proxy_set_header Host api.studenttracker.co.il;
            proxy_set_header X-Forwarded-Proto $scheme;
            proxy_set_header X-Real-IP $remote_addr;
            proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
            proxy_set_header Cookie $http_cookie;
         }
    }
}

The backend application except to receive 2 headers in order to get authorized PARAM_ID_AUTH and PARAM_X_AUTH.

While sending it, It's seem to be that the header does not arrive to the backend application at all.

I will Appreciate you help, Thanks!