How do I deploy NodeJS(backend REST API) and frontend (React) all served by Nginx

Hello,

A brief description of my stack is required, i have nodejs, react on ubuntu 18.04 . I want to use nginx to redirect all API calls to api.domain.com and also serve react on domain.com or www.domain.com. Am halfway through as i have already nginx redirecting both backend and frontend; however a problem arose i can’t make api calls from the frontend to the backend. as am getting cors Errors. more specifically the resource at api.my_domain.com has been blocked by cors policy this the nginx conf of api.domain.com

  location / {
        proxy_pass http://localhost:5001;
        proxy_http_version 1.1;
        proxy_set_header X-Forwarded-Proto https;
        proxy_set_header Upgrade $http_upgrade;
        proxy_set_header Connection 'upgrade';
        proxy_set_header Host $host;
        proxy_cache_bypass $http_upgrade;
        set $cors '';
if ($http_origin ~ '^https?://(localhost|www\.cinetie\.com|cinetie\.com)') {
        set $cors 'true';
}
if ($cors = 'true') {Connection reset by 206.189.238.61 port 22
        more_set_headers 'Access-Control-Allow-Origin' "$http_origin" always;
D:\apps\nodejs\cinetie-backend>s-Control-Allow-Credentials' 'true' always;
        more_set_headers 'Access-Control-Allow-Methods' 'GET, POST, PUT, DELETE, OPTIONS' always;
        more_set_headers 'Access-Control-Allow-Headers' 'Accept,Authorization,Cache-Control,Content-Type,DNT,If-Modified-Since,Keep-Alive,Origin,User-Agent,X-Requested-With' always;
        # required to be able to read Authorization header in frontend
        more_set_headers -s '400 422 403 404 401 500 522 503'
        more_set_headers 'Access-Control-Expose-Headers' 'Authorization' always;
}

if ($request_method = 'OPTIONS') {
        # Tell client that this pre-flight info is valid for 20 days
        more_set_headers 'Access-Control-Max-Age' 1728000;
        more_set_headers 'Content-Type' 'text/plain charset=UTF-8';
        more_set_headers 'Content-Length' 0;                                                                                                                                    return 204;                                                                                                                                                     }

So how do i fix this ?