Nginx proxy pass not working, still display Welcome to nginx

Question

in my ubuntu have 2 docker container, one is nginx, other one is gitea. I tried set nginx proxy pass to reverse proxies the gitea, but don't know why not working at all. this is my default.conf

server {
    listen       80;
    listen  [::]:80;
    server_name  www.mydomain.com mydomain.com;

    #access_log  /var/log/nginx/host.access.log  main;

    location / {
        root   /usr/share/nginx/html;
        index  index.html index.htm;
    }


    #error_page  404              /404.html;

    # redirect server error pages to the static page /50x.html
    #
    error_page   500 502 503 504  /50x.html;
    location = /50x.html {
        root   /usr/share/nginx/html;
    }

this is my git.domain.com.conf

server {
  listen 2222;
  listen 4000;
  listen [::]:2222;
  server_name git.domain.com;

  location / {
        proxy_pass http://xxx.xxx.xxx.xxx:4000;
        client_max_body_size 512M;
        proxy_set_header Host $host;
        proxy_set_header X-Real-IP $remote_addr;
        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
        proxy_set_header X-Forwarded-Proto $scheme;
  }


}

when I access the website git.domain.com, it just show Welcome to nginx! that page.

Thank you so much for helping.

Trying to reverse proxies the web, but not working.